AMENDMENT NUMBER FOUR
                                       TO
                                CREDIT AGREEMENT


         This  AMENDMENT  NUMBER FOUR TO CREDIT  AGREEMENT  (this  "Amendment"),
dated as of July 30, 1997,  is entered  into by and among  MOBILE MINI,  INC., a
Delaware corporation (the "Borrower"), each financial institution a party to the
Credit Agreement  (collectively,  the "Lenders"),  and BT COMMERCIAL CORPORATION
acting as agent for the Lenders ("BTCC"), in light of the following facts:

                                 R E C I T A L S

         A. The parties hereto have previously  entered into that certain Credit
Agreement,  dated as of March 28,  1996,  as amended by that  certain  Amendment
Number One to Credit  Agreement,  dated as of November  __,  1996,  that certain
Amendment Number Two to Credit  Agreement,  dated as of March 24, 1997, and that
certain Amendment Number Three to Credit  Agreement,  dated as of March 31, 1997
(as amended, the "Agreement").

         B.  Borrower has sold or will sell an  aggregate  amount of Six Million
Dollars ($6,000,000),  which amount shall be net of any subordinated bridge loan
proceeds,  if such bridge loans are repaid in full, of  subordinated,  unsecured
notes (the "Subordinated  Debt") pursuant to the $3,000,000 Senior  Subordinated
Promissory  Note,  dated  July 30,  1997,  (the  "Bridge  Note") by and  between
Borrower  and  Arizona  Land  Income  Corporation  ("ALIC")  and  certain  other
substantially  similar  subordinated notes by and between Borrower and ALIC (the
"Subsequent Financing").  The Bridge Loan will be paid in full upon consummation
of the Subsequent Financing.

         C. The parties hereto desire to amend the Agreement in accordance  with
the terms of this Amendment.

                                A G R E E M E N T

         NOW, THEREFORE, the parties hereto agree as follows:

         1. Defined Terms. All initially  capitalized terms used but not defined
herein shall have the meanings assigned to such terms in the Agreement.

         2. Amendment to Section 2.2.  Section 2.2(a) of the Agreement is hereby
amended by deleting the phrase  "which shall not exceed  $35,000,000"  from such
Section and replacing it with the phrase "which shall not exceed $40,000,000".

         3.  Amendment of Annex I. Annex I of the Agreement is hereby amended by
deleting  the amount of the  Revolving  Credit  Commitment  for each  Lender and
replacing such amounts as follows:

================================================================================
Lender                                           Revolving Credit Commitment ($)
================================================================================
BT Commercial Corporation                        13,333,333.34
- --------------------------------------------------------------------------------
Nationsbank of Texas, N.A.                       13,333,333.33
- --------------------------------------------------------------------------------
Deutsche Financial Services Corporation          13,333,333.33
================================================================================


         4. Subordinated Debt.

                  (a) BTCC  consents  to  Borrower's  sale of the Bridge Note to
ALIC,  and  such  sale  shall  not  constitute  an Event of  Default  under  the
Agreement.

                  (b) The Subordinated Debt shall not exceed Six Million Dollars
($6,000,000).  In the event the  Subordinated  Debt exceeds Six Million  Dollars
($6,000,000),  such  occurrence  shall  constitute an Event of Default under the
Agreement.

                  (c)  With  regard  to  Section  8.8  of  the  Agreement  only,
Borrower's sale of the  Subordinated  Debt to ALIC shall be treated as a sale of
equity securities,  and Borrower shall be subject to the terms and conditions of
Section 8.8 as a result thereof.  In addition,  with regard to the  Subordinated
Debt and its treatment as an equity security under Section 8.8 only,  during the
term of this  Agreement and so long as there is no continuing  Event of Default,
Borrower  may  carry  forward  and add to the next  year's  Capital  Expenditure
limitation  amount the unused  portion  of the  limitation  amount for the prior
year,  up to a  maximum  of one  hundred  percent  (100%)  of the  prior  year's
limitation.

                  (d) In connection with the  Subordinated  Debt, the Collateral
under the Agreement  shall exclude the Reserve  Account (as that term is defined
in the Bridge Note and as that term is defined in any other Subordinated Debt so
long as such  definition is  substantially  similar to the definition of Reserve
Account  under the Bridge  Note)  provided,  however,  the funds in the  Reserve
Account shall not exceed $375,000 at any time.

         5.  Amendment to Section 1.1.  Section 1.1 is amended by inserting  the
following  in the  definition  of  "Consolidated  Tangible  Net  Worth"  between
"Lenders"  and the  period  at the end of the  first  and only  sentence  of the
Section:

                  "provided,   however,  that  the  Subordinated  Debt  and  any
                  proceeds  thereof  shall be excluded from the  calculation  of
                  Consolidated Tangible Net Worth herein."

         6.  Amendment to Section  8.9(a).  Section  8.9(a) of the  Agreement is
hereby amended by inserting before the semicolon the following:

                  ", and Indebtedness under the Subordinated Debt".
                                       2

         7.  Amendment  to Section  8.4.  Section 8.4 is amended by deleting the
Ratios for the four  quarters  of 1998 and  replacing  such  Ratios as set forth
below:

================================================================================
                  For Quarters Ended                                 Ratio
- --------------------------------------------------------------------------------
                        3/31/98                                    2.00:1.0
- --------------------------------------------------------------------------------
                        6/30/98                                    2.00:1.0
- --------------------------------------------------------------------------------
                        9/30/98                                    2.20:1.0
- --------------------------------------------------------------------------------
                       12/31/98                                    2.35:1.0
================================================================================

         8.  Amendment  to Section 8.7.  Section 8.7 of the  Agreement is hereby
amended by deleting  such  Section in its  entirety  and  replacing  it with the
following:

                           "8.7 Minimum  Utilization  Rates.  The Borrower shall
maintain minimum  utilization  rates for each fiscal quarter,  calculated at the
end of each  such  quarter  as the  average  amount  during  such  quarter,  and
calculated as:

                           (a) (i) the  number of units of  Borrower's  Eligible
Container  Fleet  Inventory  which is then subject to valid,  current  rental or
lease agreements between Borrower and the renters or lessees thereof, divided by
the aggregate number of units of Borrower's  Eligible Container Fleet Inventory,
of not less than eighty-three percent (83%) for the second quarter of the fiscal
year ending  December  31,  1997 and  eighty-five  percent  (85%) for each other
quarter; and

                           (b) (i) the  number of units of  Borrower's  Eligible
Container  Fleet  Inventory  which is then subject to valid,  current  rental or
lease agreements between Borrower and the renters or lessees thereof, divided by
(ii) sum of (A) the  number  of units of  Borrower's  Eligible  Container  Fleet
Inventory,  and (B)  the  number  of  units  of  Borrower's  Eligible  Container
Inventory Held For Sale plus the number of units of Borrower's  Eligible Primary
Raw Materials Inventory  consisting of unrefurbished ISO units, of not less than
seventy-eight  percent  (78%) for the second  quarter of the fiscal  year ending
December 31, 1997 and eighty  percent  (80%) for each other  quarter;  provided,
that for the purposes of calculation of compliance with this Section 8.7(b), the
aggregate of the number of units of Eligible  Container  Inventory Held For Sale
plus the number of units of Borrower's  Eligible Primary Raw Materials Inventory
consisting of unrefurbished ISO units, as a percentage of the sum of clauses (A)
and (B) above, shall not exceed five percent (5%)."

         9.  Amendment to Section 8.10.  Section 8.10 of the Agreement is hereby
amended by adding to such Section the following subparagraph:

                  " (k)  Deposits  or  pledges to  support  Borrower's  interest
                  payment  obligations  under the Subordinated  Debt pursuant to
                  the terms of such  Subordinated  Debt, so long as such deposit
                  or pledge relates to an amount
                                       3

                  which does not exceed the amount equal to one six-month period
                  of  interest  on the  principal  balance  of the  Subordinated
                  Debt."

         10. Guaranties of the Subordinated Debt.  Notwithstanding  Section 8.11
of the Agreement,  the Material Subsidiaries may guarantee the Subordinated Debt
but such guaranties shall be subordinate to any guaranties or obligations by the
Material Subsidiaries in favor of the Lenders.

         11.  Conditions  Precedent.  The  effectiveness  of this  Amendment  is
subject to and conditioned upon the fulfillment of each and all of the following
conditions precedent:

                  (a) BTCC shall have received this  Amendment  duly executed by
Borrower and Majority Lenders;

                  (b) BTCC  shall  have  received  an  affirmation  letter  duly
executed by each guarantor under the Guaranties,  indicating the consent by each
such guarantor to the execution and delivery by Borrower of this Amendment;

                  (c)  BTCC  shall  have  received   payment  for  all  fees  in
connection with this Amendment from Borrower;

                  (d) BTCC shall have received  executed  replacement  revolving
promissory  notes for each  lender  under the  Agreement  in form and  substance
satisfactory  to BTCC pursuant to the amendments to the Agreement under Sections
2 and 3 herein;

                  (e) BTCC shall have  approved of the terms and  conditions  of
the Subordinated Debt (such approval not to be unreasonably withheld),  and such
Subordinated  Debt  shall  provide,  among  other  things,  subordination  terms
acceptable to BTCC in its reasonable business judgment; and

                  (f) BTCC shall have received  executed  modifications or other
necessary  documents and such title  insurance as BTCC shall require,  either by
endorsement  to the  policy  of title  insurance,  or by a new  policy  of title
insurance,  insuring  such  deed(s) of trust or  mortgages  and that the lien(s)
created  thereby  continue to be first  priority lien, all in form and substance
satisfactory  to BTCC in its sole and absolute  discretion,  and subject to such
exceptions as are approved by BTCC.

         12.  Counterparts.  This  Amendment  may be  executed  in any number of
counterparts and by different  parties on separate  counterparts,  each of which
when so  executed  and  delivered  shall be deemed to be an  original.  All such
counterparts, taken together, shall constitute but one and the same Amendment.
                                       4

         13.  Reaffirmation of the Agreement.  Except as specifically amended by
this Amendment, the Agreement shall remain in full force and effect.

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed at Los Angeles, California as of the date first hereinabove written.

                                    MOBILE MINI, INC.,
                                    a Delaware corporation


                                    By:
                                        ------------------------------
                                             Larry Trachtenberg,
                                             Chief Financial Officer


                                    BT COMMERCIAL CORPORATION,
                                    a Delaware corporation,
                                    individually and as agent


                                    By:
                                        ------------------------------

                                    Title:
                                           ---------------------------


                                    NATIONSBANK OF TEXAS, N.A.


                                    By:
                                        ------------------------------

                                    Title:
                                            --------------------------


                                    DEUTSCHE FINANCIAL SERVICES
                                    CORPORATION


                                    By:
                                        ------------------------------

                                    Title:
                                            --------------------------
                                       5

                              CONSENT OF GUARANTORS


         Each of the  undersigned,  as a guarantor of the  obligations of MOBILE
MINI,  INC., a Delaware  corporation  ("Borrower"),  arising out of that certain
Credit  Agreement,  dated as of March  28,  1996,  as  amended  by that  certain
Amendment  Number One to Credit  Agreement,  dated as of November __, 1996, that
certain  Amendment Number Two to Credit  Agreement,  dated as of March 24, 1997,
and that certain Amendment Number Three to Credit  Agreement,  dated as of March
31, 1997 (as amended,  the  "Agreement"),  among BT  Commercial  Corporation,  a
Delaware corporation ("Agent") and the lenders party thereto ("Lenders"), on the
one hand, and Borrower, on the other hand, hereby acknowledges receipt of a copy
of that  certain  Amendment  Number Four to Credit  Agreement,  dated as of July
[__],1997,  among Agent,  Lenders and Borrower,  consents to the terms contained
therein,  and  agrees  that  the  Continuing  Guaranty  executed  by each of the
undersigned  shall remain in full force and effect as a  continuing  guaranty of
the obligations of Borrower owing to Agent and Lenders under the Agreement.

         Although  Agent has informed us of the matters set forth above,  and we
have acknowledged same, we understand and agree that Agent has no duty under the
Agreement,  the  Continuing  Guaranty  or any other  agreement  between us to so
notify us or to seek an acknowledgment, and nothing contained herein is intended
to or shall create such a duty as to any advances or transactions hereafter.

         IN WITNESS WHEREOF,  each of the undersigned has caused this Consent of
Guarantors to be duly executed by its respective  authorized officers as of July
30, 1997.

                                    MOBILE MINI I, INC.,
                                    an Arizona corporation


                                    By
                                        ------------------------------

                                    Title
                                          ----------------------------


                                    DELIVERY DESIGN SYSTEMS, INC.,
                                    an Arizona corporation


                                    By
                                        ------------------------------

                                    Title
                                          ----------------------------
                                       6