RC-101 retains anti-HIV-1 activity while in the presence of vaginal fluid. HIV-1 entry indicator cells, TZM-bl, were infected either with HIV-1 BaL virus alone (V), virus in combination with pooled human vaginal fluid (VF, 1 : 20 final dilution), virus in combination with RC-101 (2 μg/ml), or virus combined with VF and RC-101 for 24 hr before luciferase measurement. Data are expressed as per cent infection and bars represent mean ± SEM, n = 4–6 for each treatment condition. *P < 0·001 versus V. **P < 0·01 versus V + VF.