PROJECT SUMMARY Cigarette smoking among adults with emotional distress (i.e. anxiety, depression) is a recognized health disparity. Individuals who smoke cigarettes and experience co-occurring emotional distress (compared to those who do not) are more dependent on cigarettes, experience more withdrawal symptoms during quit attempts, and have greater difficulty achieving abstinence. Distress intolerance (DI), or one’s inability to withstand aversive states, is a cognitive-emotional vulnerability implicated in the emotion-smoking comorbidity. Decades of empirical inquiry have focused on translating DI to a smoking cessation treatment target. However, these efforts have been met with relatively little success, which appear to reflect weaknesses in the literature’s conceptualization and assessment of DI. To address these limitations, we propose a fresh perspective on this research topic, by reconceptualizing DI as a dynamic intraindividual process that can be activated by various types of distress (e.g., physical distress like pain or fatigue), and influenced by various contextual (situational) factors. This K23 proposal outlines a well-integrated research and training plan for mentored, patient-oriented career development. The proposed research involves a multi-method approach, to understanding how DI varies on a moment-to-moment basis and the factors that influence it among people who smoke. Phase I of the project will involve a qualitative investigation. Phase II will involve quantitative examination of naturalistic momentary data via ecological momentary assessment (EMA) over a 28-day period. EMA will include randomly sampled and self-initiated reports of DI, distress and situational context during smoking. Hypotheses of momentary within-person internal and situational factors that influence momentary DI during smoking will be evaluated primarily with longitudinal modeling methods. This research plan provides the necessary landscape for experiential learning and men