BACKGROUND: Bacterial vaginosis (BV) is associated with increased risk of obstetrical and gynecologic complications and acquisition of sexually transmitted diseases. Despite this, very little is known about the pathogenesis of this disease. METHODS: Interleukin (IL)-1 beta , tumor necrosis factor- alpha , IL-6, and IL-8 concentrations in vaginal wash and serum samples from women with normal flora, intermediate flora, and BV (determined by Nugent criteria) were measured by enzyme-linked immunosorbent assay. RESULTS: Cytokine levels were not different between women with intermediate flora and women with BV. Women with either intermediate flora or BV had significantly higher concentrations of IL-1 beta in vaginal wash samples than did women with normal flora. The presence of IL-1 beta in vaginal wash samples was associated with >30 Gardnerella or Prevotella morphotypes per high-power field, as detected by Gram staining of vaginal swab specimens. Variation in the numbers of Lactobacillus and Mobiluncus species did not influence local cytokine levels. Serum cytokine levels were not influenced by any changes in vaginal flora. CONCLUSIONS: Women with intermediate flora generate significant cytokine responses. It is possible that the risks associated with BV may also affect women with intermediate flora and that appropriate treatment may reduce such risk.