Osteochondromas represent the most common primary bone tumours; they reportedly represent 20-50% of all benign bone tumours and 10-15% of all bone tumours. Malignant transformation is their most severe complication. However, deformities and interference with major joint function are the most frequent complaints in patients with hereditary multiple osteochondroma. Treatment should therefore aim not only at surgical resection of the masses but also at prevention of deformities. This article reports observations made on 69 patients with hereditary multiple osteochondroma and 313 patients with solitary osteochondroma, with a mean follow-up of 13.4 years.