The authors studied the relative contributions of psychological characteristics and rheumatoid arthritis (RA) morbidity to RA symptoms and medication side effects. Thirty-one consecutive patients attending an RA clinic completed self-report questionnaires and diaries assessing RA symptoms and somatic style, a constellation of beliefs, attitudes, and concerns about disease and health. After 3 months, the patients were assessed for RA symptoms and self-reported medication side effects. At inception, RA symptoms were associated with several components of somatic style. At 3-month follow-up, changes in RA symptoms and the incidence of medication side effects were predicted by somatic style variables measured at inception. The symptoms of RA and the side effects of RA pharmacotherapy are prospectively predicted by somatic style as well as by the severity and extent of RA.