Condom failure (slippage or breakage) has been shown to be associated with HIV seroconversion among men who have sex with men (MSM), but predictors of failure have been poorly elucidated. Of 2592 HIV-seronegative MSM participants in the HIV Network for Prevention Trials (HIVNET) multisite Vaccine Preparedness Study who reported condom use for anal sex in the 6 months before enrollment, condom failure was reported by 16.6%, with failure rates of 2.1/100 episodes of condom usage (2.5 failures/100 episodes for receptive anal sex and 1.9/100 episodes for insertive anal sex). In separate multivariate models evaluating predictors of condom failure reported by the insertive and receptive partners, more frequent condom use was associated with a decreased per-condom failure rate and amphetamine and heavy alcohol use with increased rates in both models. Being employed, having private medical insurance, and using lubricants for >80% of anal sex acts were significantly associated with decreased failure rates in the insertive model. Safer sex counseling should particularly target men of lower socioeconomic status, promote proper and consistent use of condoms with appropriate lubricants, and address the impact of drug use, especially amphetamines and alcohol, on condom failure.