The changes in serum prealbumin (transthyretin) and serum albumin in acute and chronic liver diseases were investigated. Albumin has long been used as a useful indicator of liver function but serum prealbumin has recently been noted for its clinical significance in acute liver diseases. Serum prealbumin concentrations and liver function tests (albumin, bilirubin, alanine aminotransferase) were determined on blood obtained from normal donors (n = 148) and from patients suffering from liver diseases (n = 78) such as acute viral hepatitis, chronic active hepatitis, cirrhosis and hepatoma. The mean serum prealbumin concentration in normal subjects was 29.6 +/- 4.82 mg/dl while the mean serum prealbumin concentration in patients with liver disease was greatly reduced (acute viral hepatitis = 15.3 +/- 7.4mg/dl; chronic active hepatitis = 10.2 +/- 6.6mg/dl; cirrhosis = 9.9 +/- 6.4mg/dl and hepatoma = 10.7 +/- 4.2). Albumin concentrations dropped slightly (13% compared to control) in acute viral hepatitis but dropped markedly (28% compared to control) in chronic liver diseases. The study suggests that serum prealbumin concentration might be a more sensitive indicator than albumin in assessing liver dysfunction in acute liver diseases.