EXHIBIT 5.1

                        [Stubbs Alderton & Markiles, LLP]



                                February 3, 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"),
1,000,000 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 receipt
by the Company of the purchase  price  therefor as specified in the Plan and the
applicable option agreement,  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