EXHIBIT 5.1


                 [Letterhead of Stubbs Alderton & Markiles, LLP]

August 22, 2007
IRIS INTERNATIONAL, INC.
9172 Eton Avenue
Chatsworth, CA 91311

Gentlemen:

         At your request,  we have examined the  Registration  Statement on Form
S-8 (the  "Registration  Statement") to which this letter is attached as Exhibit
5.1 filed by IRIS International,  Inc., a Delaware  corporation (the "Company"),
in order to register  under the  Securities Act of 1933, as amended (the "Act"),
1,750,000  shares  of  common  stock of the  Company  (the  "Shares"),  issuable
pursuant to the Company's 2007 Stock Incentive Plan (the "2007 Plan").

         We have  examined  originals  or  certified  copies  of such  corporate
records of the Company and other  certificates and documents of officials of the
Company,  public officials and others as we have deemed appropriate for purposes
of  this  letter.  We  have  assumed  the  genuineness  of all  signatures,  the
authenticity  of all documents  submitted to us as originals,  the conformity to
authentic  original  documents of all copies  submitted  to us as conformed  and
certified or reproduced copies.

         We are of the  opinion  that the Shares have been duly  authorized  and
upon  issuance and sale in  conformity  with and pursuant to the 2007 Plan,  and
following receipt by the Company of the consideration  therefor, the Shares will
be validly issued, fully paid and non-assessable.

         We consent to the use of this opinion as an Exhibit to the Registration
Statement.


                                         Respectfully submitted,


                                         /s/ Stubbs Alderton & Markiles, LLP
                                         ---------------------------------------
                                         STUBBS ALDERTON & MARKILES, LLP