We evaluated a new commercial latex agglutination test for herpes simplex virus antigen detection (Virogen Herpes Slide Test, Wampole Laboratories, Cranbury, N.J.). In testing of eluates from 100 lesion swabs, mostly from genital sites, the following test parameters were ascertained: sensitivity, 73%; specificity, 89%; positive predictive value, 89%; negative predictive value, 72%. Testing was also performed on 160 supernatants from 153 cell cultures inoculated with clinical samples. In this application, sensitivity and specificity were each 100%, provided supernatants were sampled for testing when the cytopathic effect involved at least 25% of the cell monolayer.