IV. Summary Inductees with a provisional diagnosis of urethral discharge were examined for the presence of Trichomonas vaginalis. Urethral specimens were provided by 926 men, of whom 735 were negroes and 191 were white. The method of demonstrating the organisms was the microscopical examination of moist films. This study revealed 144 men positive for Trichomonas vaginalis, a percentage incidence of 15.5. Separating this group into white and negro men, the percentage incidence was 12 and 16.5 respectively. Of the 926 men examined, 246 (26.5 per cent) were classed as non-specific urethritis. The incidence of Trichomonas vaginalis found in cases of non-specific urethritis was 28.7 per cent in the white group. For the negro group it was 39 per cent. The percentage incidence of non-specific urethritis cases which may be attributable to Trichomonas vaginalis was 36.9 per cent. The entire group of Trichomonas vaginalis-positive men was relatively free from all symptoms. A discharge may be noted which is characteristically small in amount, thin in consistency, and of a dirty, white color. Microscopically, this discharge showed few epithelial cells, and a moderate number of pus cells and trichomonads. Some of the stained smears were similar to vaginal ones from cases of Trichomonas vaginalis vaginitis, as to number of trichomonads and types of bacteria. The male is the important transmitter of Trichomonas vaginalis infestation, while the female eventually becomes a reservoir of infection.