OBJECTIVE: Alteration in cortisol levels has been reported in HIV infection and may be related to levels of psychiatric distress and immune function. The goals of this study were to assess cortisol levels in subjects with HIV infection and to determine whether stress-related activation of the hypothalamic-pituitary-adrenal (HPA) axis results in compromised immune function. METHOD: As part of a longitudinal study, the authors assessed urinary free cortisol levels of HIV-positive and HIV-negative homosexual men at four time points during a period of 2 years. Subjects' scores on the Hamilton depression and anxiety rating scales, medical stage of HIV infection, and CD4+ and CD8+ cell counts were also assessed. Repeated measures analysis of variance was used to determine whether subjects' cortisol levels at the four time points differed according to their serological status. Pearson correlation coefficients were computed to examine the relationships among mood ratings, cortisol levels, medical stages, and cell counts. RESULTS: Cortisol levels did not differ significantly between the HIV-positive and the HIV-negative subjects and were not associated with stage of medical illness in HIV infection. An association between cortisol level and depressed and anxious mood was found only at the first assessment. Cortisol level was not associated with CD4+ cell count in either group of subjects. CONCLUSIONS: There were no significant elevations of cortisol levels in the HIV-infected subjects, nor was there consistent evidence for stress-related activation of the HPA axis in either the HIV-positive or the HIV-negative subjects.