OBJECTIVE: The primary aim is to examine concordant/discordant results of drug use assessments in adults with schizophrenia. METHODS: Latent class analysis and multinomial logistic regression were used to examine concordance/discordance between drug use measures and identify characteristics differentiating participants across classes. RESULTS: Four classes - non-users, users, probable users, and RIA discordant - fit best. Age, sex, race/ethnicity, and psychiatric symptoms differed significantly across classes. CONCLUSIONS: Findings showed that discordance between results occurs at non-trivial rates and is, in part, attributable to individual characteristics. Results suggest the need for strategies to limit discordance and improve detection of drug use in adults with schizophrenia.