Objective: To determine the prevalence of cervical dysplasia in patients with atypical squamous cells of undetermined significance (ASCUS) Pap tests who have bacterial vaginosis (BV), compared with those without BV.Methods: This investigation was a prospective cohort study of 46 patients evaluated for ASCUS Pap tests. The prevalence of cervical dysplasia among women with BV, diagnosed by Gram stain using Nugent’s criteria, was compared with the prevalence of cervical dysplasia in women without BV.Results: Forty-one percent (19/46) of patients in the study had BV. Thirty-five percent (16/46) had cervical dysplasia. Among those with cervical dysplasia, 69% (11/16) had cervical intraepithelial neoplasia (CIN) 1, 25% (4/16) had CIN 2, and 6% (1/16) had CIN 3. An additional five patients had condyloma or human papillomavirus changes detected on cervical biopsy, increasing the percent of patients with an abnormality to 46% (21/46). Among women with BV, 5 of 19 (26%, 95% CI 0.06–0.46) had an abnormality on biopsy. In women without BV, 16 of 27 (59%, 95% CI 0.40–0.78) had an abnormality on biopsy. The relative risk of having an abnormal biopsy after an ASCUS Pap test if BV was absent, compared with if BV was present, was 2.27 (P <0.05). The ratio of low-grade dysplasia to high-grade dysplasia was similar in both groups.Conclusions: Women with ASCUS Pap tests have a significant risk of having cervical dysplasia, some of which will be high grade. Women without BV have more than twice the incidence of cervical dysplasia and abnormal cervical biopsies, compared with women with BV.