Objective: Our purpose was to evaluate the ability of the Papanicolaou smear to identify bacterial vaginosis in comparison with the Amsel clinical criteria. Study Design: We retrospectively identified 159 pregnant women screened for bacterial vaginosis with the Amsel criteria who had a contemporaneous Papanicolaou smear and negative results on screening for Chlamydia trachomatis and Neisseria gonorrhoeae. Bacterial vaginosis was identified in 45 women. We used the McNemar χ 2 test to determine discrepancies between the two screening methods for the detection of bacterial vaginosis. Results: Compared with the Amsel criteria, the sensitivity and specificity of the Papanicolaou smear for yielding a diagnosis of bacterial vaginosis were 49% (95% confidence interval, 36%-64%) and 93% (95% confidence interval, 86%-97%), respectively, with a positive predictive value of 73% and a negative predictive value of 82%. The detection of bacterial vaginosis by Papanicolaou smear was significantly different from that by Amsel criteria (P = .01). Conclusion: The Papanicolaou smear is not a reliable screening test for bacterial vaginosis during pregnancy. (Am J Obstet Gynecol 2000;182:1048-9.)