To compare the efficacy of oral versus vaginal metronidazole treatment in pregnant women with bacterial vaginosis, and to compare cytokine profiles (interleukin-1β, -6, and -8) in the cervical secretions of these women before and after treatment. Pregnant women with bacterial vaginosis diagnosed both by Gram stain and clinical criteria were randomized to receive oral (n = 52) or vaginal (n = 50) metronidazole therapy. Cervical specimens for cytokine analysis and vaginal fluid for evaluation of bacterial vaginosis were obtained at baseline and 4 weeks after treatment. There was no significant difference in therapeutic cure rates (defined as a Gram stain score of 0–3 and the absence of all four clinical signs of bacterial vaginosis) between the two groups (71% and 70% for the oral and vaginal groups, respectively, P = 1.0). Cervical levels of interleukin-1β, -6, and -8 were significantly lower after treatment among the 72 women cured of bacterial vaginosis (P < .001, P = .001, and P = .02, respectively) but not among women who failed to respond to therapy. For interleukin-1β and -6, a significant decrease in cytokine level was observed in both the oral and vaginal treatment groups. One week of oral metronidazole and 5 days of intravaginal metronidazole are equally efficacious for treatment of bacterial vaginosis during pregnancy. The decrease in cervical interleukin-1β, -6, and -8 levels among women who established a normal flora after treatment but not among those with persistent bacterial vaginosis suggests a direct linkage between vaginal flora abnormalities and elevated cervical levels of interleukin-1β, -6, and -8.