['Herpes simplex virus type 2 (HSV-2) reactivations are associated with increased HIV load, but whether HSV-2 coinfection accelerates HIV disease is unclear. We compared rates of CD4 count decline according to HSV-2 status in untreated HIV-infected adults.', 'HIV-infected patients with a past period of antiretroviral therapy (ART)-untreated follow-up with initial CD4 count of 400-900 cells/mm(3) and no chronic anti-HSV therapy were included. HSV-2 status was determined by HerpeSelect enzyme-linked immunosorbent assay. Rates of CD4 count change were compared by HSV-2 status using mixed linear regression models, and time to the first of ART initiation or CD4 <350 cells/mm(3) using proportional hazards models.', 'Of 218 patients included, 123 (56.4%) were seropositive for HSV-2 and 161 (73.8%) for HSV-1. In univariate analysis, the difference in the rate of CD4 count change associated with HSV-2 was not statistically significant at +13.6 cells/mm(3)/year (P = .12). Results were similar at -4.5 cells/mm(3)/year (P = .68) after adjustment for sex, HSV type 1, oral and genital herpes symptoms, immigrant status, and the interaction of immigrant status with time. However, HSV-2 seropositivity was associated with a shorter time to the first of ART initiation or CD4 <350 cells/mm(3), with an adjusted hazard ratio of 2.07 (95% confidence interval, 1.28-3.33).'] Does herpes simplex virus type 2 coinfection accelerate CD4 count decline in untreated HIV infection?