Purpose: To determine if ultrasound (US) of selected joints in the hands and feet can detect more erosions than radiography and establish the presence of erosive disease in patients with rheumatoid arthritis (RA). Methods: Eighty joints in ten patients with RA and 40 joints in five healthy control subjects, who were age, gender and ethnicity-matched to the patients with arthritis, were prospectively studied with radiographs and sonography. Conventional radiographs of the hands and feet were obtained. US examinations of the 2nd and 5th metacarpal-phalangeal (MCP) joints of the hands, and the 1st and 5th metatarsal-phalangeal (MTP) joints of the feet were performed. Radiographs and US exams were independently graded for the presence of erosions. Results: None of the control subjects had erosions. US detected erosions in 17/80, and radiographs detected erosions in 6/80 joints assessed with both modalities. US detected all erosions seen by radiographs in these selected joints. Erosive disease was present in the radiographs of seven of ten RA patients. US established erosive disease in eight of ten RA patients. US determined erosive disease in two of the three patients without radiographic erosions. Conclusions: US of the MTP and MCP joints in RA can detect erosions not seen with radiography and may be complementary to radiography in establishing the presence of erosive disease in early RA.