To estimate the impact of prevalent and incident herpes simplex virus type 2 (HSV-2) infection on the acquisition of human immunodeficiency virus type 1 (HIV-1), stored serum samples from a cohort of 2732 HIV-1-seronegative patients attending 3 sexually transmitted infection clinics and 1 reproductive tract infection clinic in Pune, India, were screened for HSV-2-specific antibodies. Incident HSV-2 infection was defined serologically as "recent" if a negative result of testing for HSV-2 could be documented within the previous 6 months or "remote" if >6 months had elapsed since the last negative test result. The prevalence of HSV-2 at enrollment was 43%. The HSV-2 incidence was 11.4 cases/100 person-years, and the HIV-1 incidence was 5.8 cases/100 person-years. The adjusted hazard ratios of HIV-1 acquisition from exposure to HSV-2 infection were 1.67 for prevalent HSV-2, 1.92 for remote incident HSV-2, and 3.81 for recent incident HSV-2. Recent incident HSV-2 infection was associated with the highest risk of HIV-1 in this study, which suggests that prevention of HSV-2 infection may reduce the risk of HIV-1 acquisition.