Recently a new reference interval for serum ALT, based on samples from up to 3000 healthy adult reference persons, was proposed. In the present study we performed a retrospective analysis of biochemical and histological data from 178 asymptomatic patients currently considered to have increased ALT. Forty-five patients (25%) had serum ALT levels within the new proposed reference interval. Of those, only one had normal liver histology. Of the remaining 44 patients with abnormal liver histology, 34 exhibited fatty infiltration. It is concluded that if the new proposed reference interval for serum ALT is used as "healthy" ranges, the sensitivity of this test in identifying subclinical liver disease will be decreased.