Serum parameters of calcium metabolism were measured in 32 consecutive patients with biopsy-proven cirrhosis due to either hepatitis (n = 13), alcohol abuse (n = 11), Wilson's disease (n = 3), or primary or secondary biliary cirrhosis (n = 5). All measurements were normal in the small group of patients with Wilson's disease. The serum concentrations of albumin, vitamin D-binding protein, total calcium, phosphorus, and 1,25-dihydroxyvitamin D3 (1,25-(OH2)D3) were decreased in the other patients with cirrhosis, but their mean serum concentrations of ionized calcium, 25-hydroxyvitamin D3 (25-OHD3) and free 1,25-(OH2)D3 index were normal. A slight but significant increase in the serum PTH measured using a carboxyl-terminal antiserum was found. A significant correlation was found between the serum concentration of either albumin or vitamin D-binding protein and the serum concentrations of total calcium, 25-OHD3, 1,25-(OH2)D3, and PTH but not with ionized calcium or free 1,25-(OH2)D3 index. The observed abnormalities of calcium metabolism in unselected patients with cirrhosis were mainly due to decreased protein synthesis. Only the patients with severe cirrhosis had decreased concentrations of 25-OHD3 but they were nevertheless able to maintain a normal ionized serum calcium and free 1,25-(OH2)D3 level, possibly by means of compensatory hyperparathyroidism.