We report nine cases of osteonecrosis of the knee after arthroscopic meniscectomy between 1992 and 1996. In five women and four men aged between 58 and 82 years (mean 69 years), magnetic resonance imaging (MRI) demonstrated a meniscal tear for which arthroscopic meniscectomy was performed. MRI was done between 3 days and 72 weeks after the onset of symptoms. Signs of osteonecrosis were not present on the initial MRI scan. Postoperatively, all patients experienced persistent knee pain and joint effusion. A repeat MRI scan 6-48 weeks after meniscectomy confirmed the diagnosis of osteonecrosis. In eight patients osteonecrosis was located on the medial, in one patient on the lateral femoral condyle. Our report supports the results of recent studies which have related osteonecrosis to arthroscopic meniscectomy. Further studies need to be undertaken to determine the aetiology of the osteonecrosis related to this procedure in the elderly. Until the results of these studies are available, we recommend considering carefully before performing arthroscopic procedures in the elderly.