EXHIBIT 5.1

                        [Stubbs Alderton & Markiles, LLP]



                                 August 26, 2005



IRIS International, Inc.
9172 Eton Avenue
Chatsworth, California 91311

Ladies/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"),
1,200,000 shares of common stock,  par value $0.01 per share (the "Shares"),  of
the Company  issuable  pursuant to the  Company's  1998 Stock  Option  Plan,  as
amended (the "Plan").

         We are of the  opinion  that the Shares have been duly  authorized  and
upon  issuance and sale in  conformity  with and pursuant to the Plan,  and upon
receipt by the Company of the specified  consideration,  having a value not less
than the par value thereof,  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  and to the use of our  name  in the  Prospectus  constituting  a part
thereof.

                             Respectfully submitted,

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