The purpose of this study was to assess the relationship between swelling detected on physical examination and effusion diagnosed by ultrasonography (US) in glenohumeral (GH) joints in patients with rheumatoid arthritis (RA). Fifty consecutive patients with RA entered the study and 20 healthy control persons formed a control group. Altogether 100 GH joints of the RA patients and 40 of the controls were evaluated. The clinical assessments were carried out by one doctor and the US investigations by another, and they were blinded to each other's results. The clinical examination and US gave similar results in 70 GH joints, whereas they differed in the remaining 30 GH joints. The kappa coefficient between these investigations was 0.202, showing poor agreement. These results showed poor agreement between the clinical assessment of swelling and effusion detected by US in GH joints. Therefore, US may considerably improve the accuracy of diagnosis of effusion in GH joints, which usually means synovitis in patients with RA.