Activities of the microsomal mono-oxygenases 7-ethoxycoumarin O-de-ethylase (EOC) and aldrin epoxidase (AE), together with microsomal epoxide hydrolase (EH) activity and concentrations of reduced glutathione (GSH) have been measured in liver from patients with alcoholic cirrhosis and in normals. Activities of both mono-oxygenases were significantly reduced in alcoholic cirrhosis. EOC activity (pmol 7-OH coumarin formed/mg microsomal protein/min) was 108.0 +/- 10.6 (n = 8) in normals and 60.9 +/- 11.6 (n = 8) in alcoholic cirrhosis (P less than 0.01). AE activity (pmol dieldrin formed/mg microsomal protein/min) was 58.9 +/- 9.5 (n = 11) in normal liver biopsies and 29.9 +/- 8.6 (n = 9) in alcoholic cirrhosis (P less than 0.05). Microsomal EH activity (nmol styrene glycol formed/mg microsomal protein/min) was similar in normals (39.2 +/- 4.4, n = 11) and alcoholic cirrhosis (40.5 +/- 9.1, n = 6). GSH concentrations (microgram GSH/g liver tissue) were lower (P less than 0.01) in alcoholic cirrhosis (792 +/- 73, n = 10) compared to normals (1182 +/- 76, n = 6).