In vitro studies revealed that aureomycin is trichomonicidal. 54 cases of T. vaginalis vaginitis were treated with aureomycin. The first 6 patients were used as controls. Of the 54 cases, 31 were symptomatic and non-pregnant, 11 were asymptomatic and non-pregnant and 12 were symptomatic and pregnant. Pregnant patients were insufflated on the lst-4th, 6th and 8th days of treatment using 500 mg. of aureomycin in 2 g. of powdered talc. Thereafter, a 250-mg. gelatin capsule of aureomycin was inserted into the vagina nightly for 2 wks. All other patients were insufflated on the 1st, 2d, 4th and 6th days of therapy; and thereafter, a 250-mg. gelatin capsule was inserted every other night for 2 wks. In 3 of 31 symptomatic, non-pregnant cases there was evidence of relapse or reinfection but no return of symptoms. These 3 patients were re-treated successfully. There were no recurrences among the 11 asymptomatic non-pregnant women treated. Three of the 12 pregnant cases showed evidence of reinfection or relapse following therapy. No significant toxic reactions to intravaginal aureomycin were noted. There was no demonstrable adverse effect on pregnancy. The home use of the gelatin capsule intravaginally gave no toxic reactions. 12 cases included in this series have been followed for approx. 6 mos., and only 2 have shown the reappearance of trichomonads. While the evaluation of any therapy in T. vaginalis vaginitis is notoriously difficult, the use of aureomycin appears promising.