Abstract The frequency and aetiology of aortic valve and mitral annular calcification was studied by echocardiography in 87 patients aged 35-70 on maintenance haemodialysis for a mean of 7·5 years (range 0·5-19). Aortic valve calcification (AVC) was found in 24 patients (28%) and mitral annular calcification (MAC) was found in 31 (36%). AVC was severe and produced aortic stenosis in 5 patients with a tricuspid aortic valve (mean age 51·6 years), which confirms that calcific aortic stenosis is a complication of chronic uraemia. MAC was associated with functional mitral stenosis in 1 patient. Premature AVC and MAC were associated with an increased calcium x phosphate product and long-term haemodialysis. There were no significant differences between those patients with aortic stenosis and those with AVC but no stenosis. Patients with AVC had an increased incidence of MAC and vascular calcification. Premature AVC and MAC is frequent in dialysis patients and appears to be related to abnormal calcium and phosphate metabolism and to increased mechanical stress on the valve cusps. In a small but important group of patients on long-term dialysis, premature valve calcification is severe and produces aortic stenosis, or less frequently, mitral stenosis.