A crude aqueous extract (T2) or a gel-filtration purified antigen of T. vaginalis was utilized to detect secretory antibodies in cervico-vaginal secretions by ELISA. The test was developed under optimum conditions using a rabbit anti-Trichomonas serum. Conditions established for monitoring antibodies to trichomonas in immunized rabbits were equally effective for human secretions. The crude extract was capable of assessing secretory antibodies in 45% of women with acute trichomoniasis and 43% of healthy women. The purified antigen showed a marked antigenic activity and compared to the crude antigen, testing 6 samples from infected women, detected a false positive and reduced the O.D. value of another sample by 1/4.