Abstract： Background Parathyroid hormone deficiency or resistance may cause hypocalcemia with related symptoms and signs. Lifelong treatment of calcium combined with vitamin D or its metabolites is always necessary for these patients. Here we reported a prospective and open-label trial to investigate the efficacy and safety of domestic-made calcitriol in treatment of hypocalcemia caused by hypoparathyroidism or pseudohypoparathyroidism.Methods Twenty-four patients with confirmed hypoparathyroidism or pseudohypoparathyroidism aged (36.5±11.0) years old were studied. Among them, 16 patients had idiopathic hypoparathyroidism, 2 had pseudohypoparathyroidism and 6 had hypoparathyroidism secondary to cervical surgery. Serum calcium levels were lower than 1.88 mmol/L. Oral calcitriol was administered twice or three times with elemental calcium 1.2 g per day. All patients were followed every 4 weeks throughout the 12-week period. Dose adjustments of calcitriol were based on serum and urinary calcium levels and symptoms of hypocalcemia.Results Twenty patients were included by the end of this study. Muscular weakness, cramps, extremity paresthesia, Chovestek's sign and Trousseau's sign were relieved in 76.9%, 100%, 94.4%, 93.3% and 78.9% of patients, respectively. Serum calcium, plasma ionized calcium and serum phosphorus levels were (1.54±0.25) mmol/L, (0.64±0.10) mmol/L and (2.00±0.46) mmol/L at baseline, and reached (2.20±0.20) mmol/L, (0.95±0.06) mmol/L and (1.68±0.25) mmol/L (P<0.01) at the 12th week of treatment, respectively. Eighty percent of patients were assessed as effective and 20% as partly effective. Three, four and eight patients had hypercalciuria at the 4th, 8th and 12th week of treatment, respectively, which were reduced by thiazide diuretics. The final dose of calcitriol was (1.09±0.50) μg/d.Conclusions Calcitriol combined with calcium can be used in treatment of hypocalcemia caused by hypoparathyroidism or pseudohypoparathyroidism effectively and safely. Serum and urinary calcium levels should be monitored during the course of the therapy.