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, we adopted the action perspective in our examination of the daily lives of chronic pain patients with rheumatoid arthritis. Our evaluation of patients' daily diary reports indicated that individuals played a more prominent role in shaping their positive versus their negative social worlds. The contribution of symptoms of ill health and demographic characteristics, as well as personality attributes were also examined as stable factors that predicted exposure to and appraisal of events. In addition to between-person measures, day to day variations in illness symptoms also played a key role in predicting their social experinces. Together, these findings suggest that stable person characteristics and within-person fluctuations in ill health are each tied to daily interpersonal experiences for those in chronic pain. More broadly, they 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 our social contexts. Keywords action theory; rheumatoid arthritis; chronic pain; interpersonal events Action theory asserts that individuals play a substantial role in shaping their social contexts (Brandtstadter, 1998;Lerner, 1983). Through our own behavior, we each garner reactions from those around us, and these reactions in turn influence our functioning and quality of life. To some extent, then, action theory suggests that we are masters of our own universe, generating the conditions in which we live, albeit often unwittingly. This perspective is woven throughout the literature, largely focusing on how individuals create stressful interpersonal environments that precipitate and/or maintain their poor functioning (e.g., Bolger & Zuckerman, 1995;Suls & Martin, 2005). Within the realm of mental health, Joiner and colleagues (1995;1999), for example, have reported that individuals with a propensity to seek reassurance from others report more stressful interpersonal events, which in turn contribute prospectively to elevations in their levels of depressive symptoms. In a similar vein, Hammen (1991) has found evidence consistent with her "stress generation" model of depression. Compared to those who are not depressed, depressed individuals experience a higher rate of self-generated life events, promoting future depression (e.g., Hammen, 1991 (Nelson et al., 2001).In the domain of physical health, action theory has some currency as well. Health psychologists have long recognized the importance of social environment, including social isolation and conflict, as a key predictor of disease risk and adaptation (e.g., Taylor & Repetti, 1997), The recognition has fueled interest in understanding individual differences as determinants of health and illness through t...