Objectives: This pilot was designed to study identified changes in the psychologic and physiological stress response of individuals who participated in a Mindfulness-Based Stress Reduction intervention while in treatment of substance abuse in a therapeutic community. Methods: Twenty-one participants in a residential therapeutic community received the intervention, which consisted of training in 5 mindfulness practices. Stress response was assessed by measuring awakening salivary cortisol and the Perceived Stress Scale (PSS) pre- and post-intervention. Results: Awakening salivary cortisol levels were significantly lower (P<0.0001) following the intervention. Although there was a decrease in self reported stress between the baseline measurement and the post-intervention measurement, the change in the PSS was not statistically significant (P=0.65). Conclusions: These results suggest that a Mindfulness-Based Stress Reduction intervention may influence the physiological response to stress for individuals in a therapeutic community. The results also support the use of salivary cortisol as an indicator of the stress response in this setting. Future studies are needed to determine the value of this intervention as an adjunct to therapeutic community treatment.