In 5 patients with a long clinical evolution of tetany and/or convulsions and with documented hypocalcaemia and hyperphosphatemia, low or inappropriate values of parathormone were detected. Only two of the patients had a history of subtotal thyroidectomy and all presented with basal ganglia calcification, bilateral subcapsular cataracts and prolonged QTc interval in the ECG. After one month of oral therapy with calcium and calcitriol, the values of calcaemia and phosphatemia were in a near-normal range with the exception of a patient in which that normalization was much slower and only occurred after correction of magnesaemia. In this last patient statistical correlation between QTc interval in the ECG and the calcaemia was statistically significant (P less than 0.001). We conclude that the QTc interval can be a useful and accessible index in acute situations of symptomatic hypocalcaemia.