Sixty-five outpatients with osteoarthritis of the knee and/or hip were assessed using radiographic ratings of disease severity, measures of psychologic coping, and multidimensional clinical outcomes of degree of pain and functional impairment. Disease severity accounted for little of the individual variability in clinical outcomes. Even after controlling for disease severity, psychologic variables remained strong predictors of individual differences in functional impairment and pain. Psychologic processes deserve greater clinical and research attention as potential mediators between disease severity and clinical outcome.