OBJECTIVE: To identify how frequently trichomoniasis and characteristics of bacterial vaginosis (BV) occur concomitantly in wet mount preparations from pregnant women. STUDY DESIGN: Diagnosis of trichomoniasis was predicted on visualization of the organism. Diagnosis of BV required a positive volatile (whiff) test, presence of "clue cells" and one of two minor criteria: (1) absence of lactobacilli, or (2) a pH > 4.5. Pregnant women from January 1995 to July 1997 at our clinic had wet mount/KOH preparations performed as standard prenatal care. Corresponding medical charts were analyzed for symptoms, race, BV, sexually transmitted diseases, urinary tract infections and other infections. RESULTS: Of 191 pregnant women identified, 69 had trichomoniasis. Seventy-nine percent of the 69 were African American. Fifteen percent of pregnant women (17) had concomitant trichomoniasis and BV. Irrespective of race, 35-38% of pregnant women with trichomoniasis had another sexually transmitted disease or a urinary tract infection diagnosed in that pregnancy. CONCLUSION: BV, or bacteria excess syndrome, is a frequent coinfection in pregnant women harboring Trichomonas vaginalis.