BACKGROUND Simultaneous sedative-alcohol use (SSAU) is a matter of public health concern. It is important to address the various motives individuals may have for involvement in SSAU. OBJECTIVE To explore the motives associated with SSAU. METHODS Data were collected as part of the ongoing Prescription Drug Misuse, Abuse, and Dependence study in St. Louis. For this analysis, the sample included 173 participants who reported nonmedical sedative use for more than 5 days, and use of alcohol, in the past 12 months. SSAU was defined as past 12-month use of sedatives and alcohol together/at the same time. RESULTS Past 12-month SSAU was reported by 61% of the sample. Multivariate logistic regression indicated that for every increment of one motive, participants were significantly more likely to report SSAU (adjusted odds ratio (aOR): 1.30; 95% confidence interval (CI): 1.12-1.52). Furthermore, reporting sedative use "to get high, to change mood, to relieve stress, to party, and 'just because' " was independently associated with the past 12-month SSAU. Past 12-month SSAU was also found to be significantly associated with simultaneous use of sedatives and cannabis in the past 12 months. CONCLUSIONS A higher number of motives, as well as specific motives reported for sedative use, were found to be significantly associated with past 12-month SSAU. CONCLUSIONS Findings underscore the need for considering motives in tailoring preventive interventions for reducing SSAU. It may be equally important to direct efforts toward decreasing the number of motives, as well as addressing the specific motives reported for sedative use.