The presence of bilateral basal ganglia calcification was sought in nine patients with post-operative and two patients with primary hypoparathyroidism, using computerized axial tomography (CAT) and plain skull radiographs. Calcification was detected with CAT in seven patients; five with post-operative and both with primary hypoparathyroidism, but in only one was it demonstrable on plain X-ray films. The presence of calcification appeared to be related to the duration of the disease and possibly the degree of control of serum calcium. Six of the seven patients with cerebral calcification also had cataracts. The incidence of basal ganglia calcification in hypoparathyroidism is probably much greater than previously recognized, especially in post-operative hypoparathyroidism.