In a retrospective study of liver function tests in subacute thyroiditis, 13 out of 22 patients with the disease demonstrated an elevation of alkaline phosphatase level. Less prevalent abnormalities were elevations in gamma-glutamyl transpeptidase (5 pts), alanine (4 pts) and aspartate (3 pts) aminotransferase activities. These enzyme alterations were not correlated with thyroid hormone levels, concomitant diseases, drugs or alcoholic intake, and normalized in six patients followed until recovery. A benign, short-lived and subclinical hepatic involvement is common in subacute thyroiditis.