OBJECTIVE To investigate the validity of reduced joint counts for ultrasonographic (US) assessment of joint inflammatory activity in patients with rheumatoid arthritis (RA). METHODS Ninety-four patients with RA were included. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) levels were recorded for each patient. The presence of tenderness, swelling and a subjective swelling score from 0 to 3 were assessed by two rheumatologists who reached consensus in 60 joints examined in each patient. All patients underwent an US examination by a third blinded rheumatologist, using power Doppler (PD). US joint effusion, synovitis and PD signal were graded from 0 to 3 in the 60 joints. A 60-joint count and index for effusion, synovitis and PD signal were recorded. A 6-, 10-, 16-, 18-, and two 12-joint counts and indices for US parameters that included the most frequently US involved joints were calculated for each patient. RESULTS A 12-joint assessment for effusion, synovitis and PD signal, including bilateral wrist, second and third MCP, second and third PIP of hands and knee joints highly correlated with corresponding 60-joint US counts and indices. This reduced-joint US evaluation showed a similar correlation with clinical and laboratory parameters of disease activity to corresponding 60-joint assessment. CONCLUSIONS We propose that a 12-joint evaluation may be a useful tool for US assessment of overall joint inflammatory activity in RA.