PURPOSE: To assess the MR findings of symptomatic osteochondromas. MATERIALS AND METHODS: We evaluated 31patients who between July, 1994 and May, 1997 underwent MR imaging for symptomatic osteochondroma. Fourteen were males and 17 were females, and their ages ranged from 8 to 49(mean, 23) years. Using T1WI, T2WI andgadolinium-DTPA-enhanced T1WI, images were analysed according to signal intensity in the osseous component of theosteochondroma, thickness of the cartilage cap, and associated change in surrounding soft tissue. RESULTS:Clinical manifestations included a palpable mass or tendency to grow(n=22) and pain on movement(n=9).Complications were of three types : that which followed change in the osseous component of the tumor, associatedchange in surrounding soft tissue, and malignant transformation. In the osseous component, bone marrow edema orcontussion was seen in 21 cases(67.7%), and in two(65%), fracture was observed. In surrounding soft tissue, muscleimpingement was seen in 21 cases(67.7%), bursitis was in 7 cases(22.6%), tenosynovitis in seven(22.6%), andvascular compression in five(16.1%). In three cases(9.7%), thansformation to chondrosarcoma had occurred ; two ofthese were derived from osteochondromatosis and one from a single osteochondroma. The thickness of the cartilagecap was as follows : <5mm(n=16), 5-10mm(n=12), and > 10mm(n=3). CONCLUSION: In patients with symptometicosteochondroma, MR imaging is useful for detecting both complications and malignant transformation.