Human subjects protection policies developed for pharmaceutical trials are now being widely applied to psychosocial intervention studies. This study examined occurrences of serious adverse events (SAEs) reported in multicenter psychosocial trials of the National Institute on Drug Abuse Clinical Trials Network. Substance-abusing participants (N = 1,687) were randomized to standard care or standard care plus either contingency management or motivational enhancement. Twelve percent of participants experienced 1 or more SAEs during the 27,198 person-weeks of follow-up. Of the 260 SAEs recorded, none were judged by the data safety monitoring board to be study related, and there were no significant differences between experimental and control conditions in SAE incidence rates. These data underscore the need to reconsider the rationale behind, and appropriate methods for, monitoring safety during psychosocial therapy trials.