100 patients who had had unilateral meniscectomy were examined some years (mean 24.8) after operation to compare the condition of their operated knees with that of their unoperated knees. Chondrocalcinosis (CC) was detected by X-ray in 20% of operated knees and in 4% of unoperated knees. In 16 patients CC was confined to the operated knee. The frequency of CC increased with age, rising in operated knees from 16.7% (less than 50 years) to 31.6% (greater than 65 years). Inflammatory features (stiffness [p less than 0.01], effusion [p less than 0.01], acute attacks [p less than 0.01]) and more severe X-ray changes of osteoarthritis were more common when CC was present. Wrist CC was present in 4 patients, and in 2 of these there had been previous trauma. CC was observed in only 3 knee radiographs from 100 age and sex matched controls. This study supports the hypothesis that calcium salts may be deposited locally in altered or damaged cartilage and may then cause further inflammation and joint damage via an amplification loop mechanism.