A series of 113 osteochondromas were treated in our institution with a long-term follow-up. A retrospective study of the cases of solitary osteochondroma diagnosed and treated in our center from 1970 to 2002 was done. A diagnosis for clinical findings in 73% of the patients was made. The most frequent location was the distal femur. Six patients had a recurrence and in two patients the lesions became malignant and chondrosarcoma developed. Relapse of the exostosis is rare, occurring in an estimated 2% of the resections. The growth of an osteochondroma and/or the presence of pain in older patients suggest possible malignancy.