A cohort of 217 human immunodeficiency virus type 1 (HIV-1)-seropositive women was observed prospectively from 1996 through 2000 to determine the frequency of genital herpes simplex virus type 2 (HSV-2) disease (symptomatic and asymptomatic) and to correlate those findings with HIV-1-related immunosuppression (absolute CD4 cell counts and plasma HIV-1 RNA levels). Participants underwent twice-yearly pelvic examinations, including cultures of cervicovaginal specimens and swab specimens from genital lesions, if lesions were present. Of the participants, 72 (33%) had genital HSV-2 infection diagnosed on the basis of either history alone (23 [32%]) or positive culture results (49 [68%]). The 72 women who had genital herpes diagnosed completed 242 total visits. Of these visits, positive HSV-2 culture results were noted at 80 (33%); at 23 (29%) of the 80 visits at which there were HSV-2-positive cultures, culture results were not associated with a clinically apparent genital lesion. Positive HSV-2 culture results occurred more frequently for samples obtained from patients with higher plasma HIV-1 RNA levels (P=.019) and lower CD4 cell counts (P<.001).