Sixty-seven patients with symptomatic knee osteoarthritis (OA) (26 male, 42 female, mean age 62.7 years) have been followed prospectively for a mean of 67.3 months (range 60-72 months). Hand radiographs were obtained at entry and at follow-up. Scintigraphic images of the hands were obtained at entry, and the predictive value of scan abnormalities for subsequent radiographic change was examined. Forty-six of 203 scan-positive joints at entry showed radiographic change, compared with 41 of 2075 scan-negative joints (P < 0.0001). The thumb base was more often involved than other joints and scintigraphy was a better predictor of change at this site than at other joints in the hand. This study confirms the predictive value of scintigraphy in hand OA and suggests that thumb base and interphalangeal joint OA behave differently.