PIP: Most cases of infectious vaginitis are accounted for by nonspecific vaginitis (NSV), which causes 40-50%; candidiasis, which causes 20-30%; and trichomoniasis, which causes 20-30%. Common reasons for failure to relieve symptoms include diagnostic errors, and sexual reinfection, but nonsexual recurrence, drug resistance, or depressed host immunity may also be responsible. Most infections can be identifed and cured if the pathophysiology of a vaginal discharge is understood and the proper diagnostic steps taken. The components of a vaginal discharge include water, electrolytes, epithelial cells, microbial organisms, organic fatty acids, proteins, and carbohydrate compounds. In most women the overgrowth of potentially pathogenic organisms is prevented by a poorly understood interreaction between lactobacilli and other organisms in the normal vaginal flora. A specific diagnosis of cervicitis, trichomoniasis, NSV, candidiasis, or normal vaginal discharge can be made on the basis of physical examination of the vulva; the location, color, viscosity, consistency, and presence on the vaginal walls of vaginal discharge; the cervical discharge; elevated vaginal pH; and fishy amine odor. Based on these findings microscopic observation can be directed toward a specific diagnosis. The presence of lactobacilli, white blood cells, trichomonads, clue cells, and Candida organisms should be sought; the appropriate conditions for observation and interpretation of findings are discussed. Instructions are provided for the preparation of cervical cultures for N. gonorrhoeae and C. trachomatis, which should be obtained when purulent cervical exudate or purulent vaginal discharge is present. Further information on the etiology, diagnosis, and treatment of physiologic vaginal discharge and the specific infections including candidiasis, trichomoniasis, NSV, and cervicitis is provided.