BACKGROUND: Little is known about the impact of episodic treatment of herpes on human immunodeficiency virus type 1 (HIV-1). METHODS: Women from Ghana and the Central African Republic who had genital ulcers were enrolled in a randomized, double-blind, placebo-controlled trial of acyclovir plus antibacterials and were monitored for 28 days. Ulcer etiologies and detection of lesional HIV-1 RNA were determined by polymerase chain reaction (PCR). Cervicovaginal HIV-1 RNA and herpes simplex virus type 2 (HSV-2) DNA and plasma HIV-1 RNA were quantitated by real-time PCR. Primary analyses included 118 HIV-1-infected women with HSV-2 ulcers (54 of whom were given acyclovir and 64 of whom were given placebo). RESULTS: Acyclovir had little impact on (1) detection of cervicovaginal HIV-1 RNA (risk ratio [RR], 0.96; 95% confidence interval [CI], 0.8-1.2) at day 7 of treatment, (2) the mean cervicovaginal HIV-1 RNA load (-0.06 log(10) copies/mL; 95% CI, -0.4 to 0.3 log(10) copies/mL) at day 7 of treatment, or (3) the plasma HIV-1 RNA load (+0.09 log(10) copies/mL; 95% CI, -0.1 to 0.3 log(10) copies/mL) at day 14 of treatment. At day 7, women receiving acyclovir were less likely to have detectable lesional HIV-1 RNA (RR, 0.70; 95% CI, 0.4-1.2) or cervicovaginal HSV-2 DNA (RR, 0.69; 95% CI, 0.4-1.3), had a lower quantity of HSV-2 DNA (-0.99 log(10) copies/mL; 95% CI, -1.8 to -0.2 log(10) copies/mL), and were more likely to have a healed ulcer (RR, 1.26; 95% CI, 0.9-1.9). CONCLUSION: Episodic therapy for herpes reduced the quantity of cervicovaginal HSV-2 DNA and slightly improved ulcer healing, but it did not decrease genital and plasma HIV-1 RNA loads. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT00158483 .