The effects of cortisol and testosterone on calcium metabolism in the hepatic bile system were investigated in thyroparathyroidectomized rats. A single subcutaneous administration of cortisol (0.1 mg/100 g) or testosterone (0.1 mg/100 g) caused a significant fall in serum calcium and a corresponding increase in liver calcium. On the other hand, the excretion of calcium into the bile after a single intraperitoneal injection of calcium chloride (4.0 mg Ca/100 g) was markedly increased by the administration of cortisol (0.1 and 1.0 mg/100 g) or testosterone (0.1 and 1.0mg/100 g). However, the bile calcium excretion was not significantly altered by the administration of thyroxine (0.1 and 1.0 mg/100 g) or vitamin D3 (20 and 100 μg/100 g). The present results suggest that the hypocalcemic effect of cortisol or testosterone is partly based on the stimulation of calcium excretion into the bile by the hormones.