From all blood donors screened within a given period of 6 months for SGPT (ALT) immediately before donation, 166 (141 male, 25 female) were found to have SGPT activities above our cutoff value of > 28 IU/l (25 degrees C). In order to define the characteristics of these blood donors they were asked for detailed medical history followed by a thorough physical examination and further serologic and biochemical testing. Factors associated with elevated SGPT activity included daily alcohol consumption (82 donors), infections associated with abnormal DCs (23), therapy with hepatotoxic drugs (8), infections that had been treated with antibiotics (6), strenuous physical exercises (5), body building supported by anabolics (2), acute HBV infection (1), acute HCV infection (1), alcohol/drug abuse and positive test for anti-HCV antibodies (1), anti-CMV positivity with absolute and relative lymphocytosis (1). In 36 cases factors that could have been associated with an increased SGPT activity were not verified. A critical valuation of the presently accepted cutoff value of 45 IU/l (25 degrees C) is given.