PURPOSE: It is difficult to determine objectively therapeutic response in rheumatoid arthritis. This study was carried out in order to assess the feasibility of MR imaging to determine disease status following antirheu-matoid medication. MATERIALS AND METHODS: Eight patients with rheumatoid arthritis underwent MR studies before treatment and approximately one year after the beginning of antirheumatoid medication. Coronal images were obtained, using a T1- and T2-weighted spin echo(n=8), contrast-enhanced T1-weighted images(n=8) and dynamic contrast-enhanced images(n=4). Bone erosions, synovial hypertrophy and bone marrow enhancement in pre- and post-medication studies were compared. On dynamic study, enhancement ratio(E) of pannus was measured(E=SNR at 30sec/SNR at precontrast). Changes of MRI findings and enhancement ratio between pre- and post-medication were compared with disease status as assessed by clinical index. RESULTS: In three patients, improvement of bone marrow edema and synovial hypertrophy was noted, and in addition, there was no evidence of newly developed boneerosion. In two of these patients, complete remission was noted on the basis of the ARA criteria. In another three patients, despite improvement of bone marrow edema and synovial hypertrophy and improved clinical parameters including morning stiffness and ESR, discrete and newly developed bone erosions were noted. In one patient with apoor response to antirheumatoid medication, aggravation of bone marrow edema and synovial hypertrophy was seen, but no definite change in bone erosions was noted. In the remaining one patient, no remarkable changes were seenin bone marrow edema, synovial hypertrophy or bone erosion. Clinically this patient showed no morning stiffness or elevated ESR. The enhancement ratio of pannus decreased in all 4 cases, especially where there were complete remission. CONCLUSION: Synovial extent, bone marrow enhancement, bone erosions and enhancement ratio of pannusmay be good parameters for monitoring disease activity in the follow-up of the patients with rheumatoid arthritis.