Determination of the synovial membrane volume in the rheumatoid arthritis (RA) wrist by gadolinium-DTPA-enhanced MRI is introduced. Moreover, dynamic imaging and an MRI score of synovial hypertrophy, based on gradings in six regions, are evaluated as substitutes of the time-consuming volume calculations. Twenty-six RA wrists were examined. Synovial membrane volumes ranged from 1 to 20 ml (median 9 ml). Synovial hypertrophy scores were highly correlated to synovial volumes (Spearman r = 0.88; P < 10(-8) for uncorrelated values). The volumes and scores were significantly higher in wrists with joint swelling and/or joint tenderness than in wrists without these signs (Mann-Whitney, both P < 0.05). Suboptimal slice selection made dynamic imaging uninformative. MRI allows quantification of the synovial volume in the rheumatoid wrist. The volume is related to clinical signs of inflammation, but may also give information about the cumulated synovial proliferation in the joint. An easily obtained score of synovial hypertrophy reflects the synovial volume and may thus be a useful marker of synovial involvement.