The use of musculoskeletal ultrasonography (US) is widely established in patients with rheumatoid arthritis (RA). Grey-scale (GS) and power Doppler (PD) are more sensitive in detecting synovitis than clinical examination. This increased sensitivity has led to the application of US also in patients with early-onset arthritis, to improve the certainty of diagnosis and to give prognostic information, while the use of US for classificative purposes has been proposed but not yet defined. US has proven its value also in patients in clinical remission, in which the presence of PD predicts radiographic progression and relapse. There is still a debate on the optimal number of joints to be scanned in patients with RA and several US scores have been proposed so far. US has therefore a relevant role in the management of RA patients, and the ongoing developments of this technique will probably lead to its wider application.