PURPOSE: To evaluate the changes and remission of disease activity with changes in inflamed synivial volumes of rheumatoid joints after therapy. MATERIALS AND METHODS: Seven rheumatoid arthritis patients who had been treated with antiinflammatory drugs were followed up. Using NIH imaging and a segmentation technique, pre- and post-enhanced images were measured in subtracted images. Intra- and interobserver variation were evaluated by two radiologists(A and B), using two independent measurements. For comparison, the cases were assigned to one of two groups : remission and non-remission. Changes in ESR and total joint counts(TJC) after therapy were compared with inflamed synovial volumes. RESULTS: Intraobserver variations were 3.2% and 2.7% in A and B, respectively, interobserver variation between A and B was 7.1%. Changes in inflamed synovial volumes correlated well with those in ESR (r=0.88, p<0.009) and TJC (r=0.78, p<0.037) after therapy. Changes between the remission and non-remission group were insignificant, however. CONCLUSION: Changes in inflamed synovial volumes reflect those in the activity of rheumatoid arthritis between pre- and post- treatment. This technique may be used as a tool for predicting therapeutic response in rheumatoid arthritis cases. Changes in inflamed synovial volumes are of limited value, however, in predicting the remission of rheumatoid arthritis after therapy.