EXHIBIT 5.1
                                   -----------

                   Opinion of John L. Gardner, General Counsel

                                November 26, 1997


Inter-Tel, Incorporated
120 North 44th Street, Suite 200
Phoenix, Arizona 85304-1822

                     Re: Registration Statement on Form S-8
                         ----------------------------------


Ladies and Gentlemen:

In  connection  with the  registration  under  the  Securities  Act of 1933 (the
"Securities  Act")  pursuant  to a  Registration  Statement  of  Form  S-8  (the
"Registration Statement") of 2,900,000 shares (the "Shares") of Common Stock, no
par value, of Inter-Tel,  Incorporated,  an Arizona corporation (the "Company"),
under the Company's  Inter-Tel,  Incorporated 1997 Long-Term  Incentive Plan and
Inter-Tel,  Incorporated 1997 Employee Stock Purchase Plan (the "Plans"),  I, as
General Counsel of the Company, have examined the Registration  Statement,  such
corporate records,  certificates and other documents, and such questions of law,
as I have considered  necessary or appropriate for the purposes of this opinion.
Upon the basis of such  examination,  I advise  you that,  in my  opinion,  when
issued  and sold in the  manner  described  in the  Plans  and  pursuant  to the
agreements  which  accompany  each  grant  under the Plans,  the Shares  will be
legally and validly issued, fully paid and assessable.

The foregoing  opinion is limited to the laws of the state of Arizona,  and I am
expressing no opinion as to the effect of the laws of any other jurisdiction.

I do  hereby  consent  to the  filing  of  this  opinion  as an  exhibit  to the
Registration Statement and any amendments thereto.



                                              Very truly yours,


                                              /s/  John L. Gardner
                                              --------------------
                                              John L. Gardner, General Counsel
                                              INTER-TEL, INCORPORATED
                                       8