1. Somatomedin (SM; sulphation factor) activity was estimated by a chick-cartilage assay in fasting sera from twenty-one patients with chronic liver disease.
2. Low SM values were found in nine out of the ten patients with cirrhosis and in two other patients, one with hepatofibrosis and one with hepatoma.
3. In general, the lowest serum SM activities were found in those patients with the most severe disease and significant correlations were found between serum SM and serum albumin, alkaline phosphatase and bilirubin.
4. Growth hormone was also measured in the samples and concentrations above 10 units/ml were found in seven patients, all of whom had reduced serum SM activities.
5. These findings indicate that low serum SM activity in liver disease is not related to growth hormone deficiency and suggest that the liver may be an important site for SM synthesis in man.