The EXPLORE study evaluated a behavioral intervention to prevent HIV infection among MSM. We examined depressive symptoms, utilization of mental health care, substance use and HIV risk taking behaviors in YMSM aged 16-25 years compared with their older counterparts. YMSM were more likely to report depressive symptoms (OR = 1.55) and less likely to report use of counseling (OR = 0.39) or medication (OR = 0.20) for psychiatric conditions. YMSM were more likely to report heavy alcohol and drug use. YMSM more often reported engaging in unprotected insertive (OR = 1.60) and receptive (OR = 2.07) anal intercourse with presumed HIV-uninfected partners, and unprotected receptive (OR = 1.72) anal intercourse with partners of unknown-HIV status. These findings suggest the need for more appropriate and accessible mental health care and substance use services for YMSM. Additionally, HIV prevention work with this population should provide comprehensive education about HIV testing and risk reduction counseling that focuses on communication about serostatus and safety in sexual situations.