1. Hepatic total glutathione (reduced plus oxidized) and oxidized glutathione levels were measured in operative wedge liver biopsy specimens obtained from 70 patients. 2. The effects on hepatic reduced glutathione (GSH) level of four potential risk factors (abnormal liver histology, abnormal preoperative tests fo liver function, drug ingestion and protein malnutrition) were examined. 3. Each of the four risk factors was associated with a significant reduction in hepatic GSH. Multivariate analysis indicated that only three of these risk factors (abnormal liver histology, drug ingestion and protein malnutrition) had independent effects in reducing hepatic GSH. 4. Twenty-five of the 70 patients studied did not have any of the four risk factors. The mean hepatic GSH level in these patients was 3.92 mumol/g of liver wet weight (SD 0.62), giving a 95% reference range of 2.71-5.14 mumol/g of liver net weight.