A meta-analysis of 8 randomized trials (1792 patients, 2947 patient-years of follow-up) showed that acyclovir (> or = 3200 mg/day) offered a significant survival benefit (P = .006 by log-rank test) in human immunodeficiency virus (HIV) infection. The treatment effect did not vary significantly in patient subgroups of different CD4 cell counts, hemoglobin levels, age, race, and sex, and with or without AIDS diagnosis. Acyclovir treatment (hazard ratio, 0.78; 95% confidence interval [CI], 0.65-0.93), higher CD4 cell count (P < .001), higher hemoglobin level (P < .001), and younger age (P < .001) reduced the hazard of mortality. Acyclovir decreased herpes simplex virus infections (odds ratio [OR], 0.28; 95% CI, 0.21-0.37) and varicella-zoster virus infections (OR, 0.29; 95% CI, 0.13-0.63) but not cytomegalovirus disease or mortality from lymphoma or Kaposi's sarcoma. A survival advantage was seen specifically in studies with high incidence of clinical herpesvirus infections (> or = 25% per year). Given the wide confidence intervals, the small effect in low-risk patients, and recent changes in HIV therapeutics, the results should be interpreted cautiously, but the meta-analysis supports the importance of pathogenetic interactions between herpesviruses and HIV.