During the last 6 months of 1955 and the first 3 months of 1956 leptospirosis antigen prepared by a commercial veterinary establishment has been available for use at the Iowa Veterinary Medical Diagnostic Laboratory on an experimental trial basis. The antigen was prepared according to the method described by Stoennerl and used as a rapid plate agglutination test. For a period of a few weeks antigens of L. pomona, L. icterohemorrhagia, and L. canicola were simultaneously available for use. During this period all bovine and swine blood samples received for leptospirosis testing were routinely tested with each of the three antigens. In other words, each and every blood sample received three separate tests for leptospirosis. Tabulation of the results secured by the testing procedure are summarized in the following tables.