Osteocalcin, a recently identified protein, is produced by osteoblasts in the bone tissue. Its plasma level is a good marker of bone metabolism and is reduced in the presence of 'osteodystrophia', commonly found in cholostatic liver diseases. We assayed plasma osteocalcin levels in 20 cirrhotic patients and compared the values with those of 22 healthy controls. In the same patients we also measured the liver function, clotting and mineral metabolism indexes and calcitonin plasma levels. Osteocalcin levels were significantly lower in liver disease patients than in controls (5.53 ng/ml S.D. 2.57 vs 7.79 ng/ml S.D. 2.23; p less than 0.01) and calcitonin plasma levels were much higher in cirrhotics (130.18 pg/ml S.D. 212.30 vs 28.9 pg/ml S.D. 13.09; p less than 0.05). We think that the low osteocalcin levels observed in cirrhotics may be a consequence of "hepatic osteodystrophy" due to low vitamin D and calcium plasma levels.