This study describes the mental health of a large cohort of gay men participating in the Chicago Multicenter AIDS Cohort Study/Coping and Change Study. Six biannual questionnaires were self-administered between 1984 and 1988. General mental health was determined by the Hopkins Symptom Checklist (HSCL). An abbreviated version of the Center for Epidemiologic Study Depression Scale (CESD-5) and an adapted Diagnostic Interview Schedule (DIS) question also measured depression. Suicidal ideation was assessed by one question in the HSCL. AIDS-specific distress was determined by three subscales specifically developed for this study While mean HSCL and CESD-5 scores were stable during the observational period, AIDSspecific distress increased over time. The HSCL scores for the cohort were somewhat elevated above general population norms but considerably below psychiatric outpatient norms. Fewer than 12% of the men reported elevated HSCL or CESD-5 scores three or more times. A self-reported episode of depression of two weeks or more, measured by the DIS screening question, was experienced by 40.1% of the sample. Suicidal ideation was reported on three or more visits by 18.8% of the men The younger members of this cohort exhibit greater general and AIDS-specific distress. Income was inversely associated with general distress. HIV-seropositive participants had generally higher AIDS-specific distress scores than those who were seronegative, but their scores were equivalent on the HSCL and CESD-5