Mitral annulus calcification, a common lesion of the elderly (over age 60 years), has been detected with increased frequency and at younger ages in patients with uraemia. To date a pathogenic role for dialysis and secondary hyperparathyroidism has been suggested only on the basis of older dialytic age and increased serum iPTH observed in the affected individuals. Because this is a potentially dangerous lesion we deemed it useful to evaluate more completely the respective roles of possible pathogenetic factors in uraemic individuals. Evaluation included echocardiography, ECG, limb radiography, and serum assays. A total of 225 dialysis (HD) patients, 67 chronic renal failure (CRF) patients on conservative treatment and 67 normal subjects were studied. Mitral annulus calcification was detected in 87 of 225 (38.6%) HD patients, 11 of 67 (16.4%) CRF and six of 67 (8.9%) normals. In HD, patients with calcification were older and on longer-term renal replacement therapy compared to those without calcification. They also had greater values of iPTH, BGP, AP, and Rx score of secondary hyperparathyroidism. Mitral annulus calcification was associated more frequently (chi 2 = 14.8; P < 0.0001) with rhythm and cardiac conduction defects, but not with ectopic calcifications. Multiple stepwise regression analysis, with mitral annulus calcification score as dependent variable, selected dialysis duration, age, and iPTH (rm = 0.368) as the most predictive parameters, with the first two carrying most of the information. The stratification of patients according with these two parameters showed a progressive increase in the frequency of calcification both with HD duration and age.(ABSTRACT TRUNCATED AT 250 WORDS)