The purpose of this study was to test the relationships between and among the concepts of severity of illness, dependency, uncertainty, functional status and the mediators of self-esteem and mastery relative to the outcome of wellbeing. The conceptual framework was adapted from various sources in the literature which support the concept of wellbeing as an important outcome in arthritis. Evidence also supports self-esteem and mastery as mediators of the chronic illness experience. Dependency, uncertainty and functional status have been shown to be predictors of wellbeing but have never been tested as a complete paradigm. The sample for the study was 128 patients with either rheumatoid arthritis or osteoarthritis. Subjects completed 7 questionnaires which measured the 7 variables under study. Descriptive statistics were used to examine the demographic characteristics of the sample. Multiple regression technique was used to empirically test the predicted theoretical concepts and to estimate predictive validity for the theoretical concepts. The results demonstrated that when self-esteem was used in the causal model, 58% of the variance in wellbeing was explained by self-esteem and uncertainty. When mastery was included instead of self-esteem 52% of the variance of wellbeing was explained by mastery and uncertainty. When tested as mediators, both self-esteem and mastery emerged as significant mediators of dependency, uncertainty and functional status relative to wellbeing. These results are of clinical use to nurses who, by virtue of working with these patients on a daily basis, are in a position to intervene with actions which encourage positive self-esteem and maintain mastery over the environment. If these actions are successful, then wellbeing can be maintained for those patients diagnosed with arthritis.