A self-report measure of rheumatoid arthritic activity developed from the articular index described by Thompson, Silman, Kirwan, and Currey (1987), was tested for reliability, validity, and sensitivity to therapeutic change. Concurrent validity was demonstrated by a significant correlation, (ICC = 0.83) between the self-report measure and a standard Thompson index completed by a rheumatologist. Test-retest reliability was demonstrated by significant correlations (ICC = 0.88, ICC = 0.77) between repeated administrations of the self-report form in 2 independent samples. The self-report measure demonstrated sensitivity to therapeutic change when completed by patients both before and after intraarticular corticosteroid injection. The rheumatologist's index correlated significantly with C-reactive protein but the self-report form did not.