Action theory proposes that individuals actively shape and then respond to their environments, highlighting the role of stable person characteristics in the development and maintenance of life's interpersonal difficulties. In this study, the authors adopt the action perspective in their examination of predictors of daily interpersonal events among chronic pain patients with rheumatoid arthritis. They probe the extent to which stable symptoms of illness explained between-person variation, and fluctuating symptoms explain day-to-day variation in both positive and negative events. Their evaluation of patients' daily diary reports indicate that between-person differences accounted for more variance in the occurrence of positive events relative to negative events (48% vs. 31%, respectively). Likewise, between-person factors accounted for more variance in appraisals of positive compared to negative events across relationship domains. Both intractable illness symptoms and disability, and daily fluctuations in pain and fatigue, were only weakly related to patients' reports of their interpersonal experiences. Consistent with action theory, these results suggest that stable person characteristics are strongly related to daily stressors and particularly daily positive events in pain patients, but still account for less than 50% of the variance in events and their appraisals. In contrast, elevations in illness-related features, both between individuals and within individuals from day-to-day, are not robust predictors of positive or negative social exchanges. These findings point to the value of capturing the experiences of individuals intensively over time, an approach that can help to elaborate the contributions of both stable factors and circumstance in shaping social contexts in chronic illness. © 2006 Wiley Periodicals, Inc. J Clin Psychol 62: 1097–1113, 2006.