Trichomoniasis is a disease of the pregnancy, but apparently not of either the cow or the bull, except in the case of postcoital pyometra. Its self-limiting nature in the cow and chronic nature in the bull mean that a positive diagnosis for the herd can more easily be obtained from bulls than from cows. Incubation of preputial scrapings or washings (or pyometritic fluid, if available) in a selective growth medium such as the InPouch system is the diagnostic method of choice. The diagnosis is based on identification of the morphology and characteristic rolling motility of the trichomonad. "High tech" molecular approaches may eventually offer greater diagnostic sensitivity than can culture methods, but currently they are no more accurate. In addition, serologic screening of the female herd (but interestingly, not the bulls) may become possible and may allow the practitioner to at least determine whether exposure has occurred in an unvaccinated herd. Control in an infected herd involves no pharmacologic treatment but rather culling of infected bulls, retention of younger, culture-negative bulls, and segregation of the female herd by reproductive status.