Objective: Rurally situated African Americans suffer from stress and drug-related health disparities. Unfortunately, research on potential mechanisms that underlie this public health problem have received limited focus in the scientific literature. This study investigated the physiological impact of nicotine and alcohol use on dehydroepiandrosterone (DHEA) functioning, a biomarker previously linked to hypothalamic-pituitary-adrenal functioning. Method: A rural sample of African American emerging adults (n = 84) completed a battery of assessments and provided six samples of salivary DHEA at wakeup, 30 minutes postwakeup, 90 minutes postwakeup, 3:00 p.m., 3:30 p.m., and 4:30 p.m. Results: Participants had more DHEA on waking as a function of smoking greater number of cigarettes throughout the day. Although this effect was not replicated with increased levels of alcohol consumption, the interaction between cigarette and alcohol use was associated with increased levels of DHEA on waking. Conclusion: While use of a single substance (i.e., cigarettes) was related to higher DHEA and greater hypothalamic-pituitary-adrenal activation, the addition of a second substance (i.e., alcohol) shifted the individual toward the hyperactive arousal profile common within chronically stressed or challenged populations. These findings support the need to further investigate the relationship between polysubstance use and physiological functioning that may be linked to known health disparities in the African American community.