We studied 229 patients with biopsy verified liver disease and compared the plasma levels of alpha 1-antichymotrypsin and alpha 1-antitrypsin. We found a significant overall correlation between alpha 1-antichymotrypsin and alpha 1-antitrypsin levels (r = 0.50, p less than 0.001). The strongest correlations were found in patients with chronic active hepatitis (r = 0.76, p less than 0.0001) and alcohol hepatitis (r = 0.60, p less than 0.001). Several clinical subgroups lacked correlation. Unexpectedly high alpha 1-antichymotrypsin values were found in patients with venous congestion. We also used the alpha 1-antichymotrypsin/alpha 1-antitrypsin ratio as a tool to identify PiZ carriers (intermediate alpha 1-antitrypsin-deficiency, PiZ). The sensitivity and predictive values were low and did not exceed that obtained by the simple use of an isolated alpha 1-antitrypsin determination. A small subgroup with low alpha 1-antichymotrypsin/alpha 1-antitrypsin ratio included patients with chronic active hepatitis of unknown etiology. Hypo-alpha 1-antichymotrypsinemia may be secondary to the liver disease per se or be an expression of an abnormal genetic trait.