The lactate and pyruvate levels, as well as acid and alkaline phosphatase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, glutaminic acid-oxalacetic acid transaminase and aldolase levels of rat liver homogenizates were measured at 24 degrees C and 38 degrees C during 120 min ischaemia from 0 to the 120th min. With the exception of transaminase and aldolase, the other enzymes were also enzyme-histochemically studied. The early lesions of the liver can be detected, both the quantitative laboratory tests and enzyme histochemical studies. The deviations from normal, observed at 24 degrees C between the 60th and 100th min, and at 38 degrees C between the 30th and 60th min, might be signs of irreversible lesions. Fractionated study of the liver homogenizate improves the assessability of enzyme determinations. In the course of "warm" ischaemia, the liver lysosomal lesions are early symptoms. Parallel to the breakdown of aerobic glycolysis lactic acid, fermentation, and an active pentose phosphate cycle can be detected. Quantitative testing of the liver homogenizate and enzyme histochemical observation of the hepatic tissue, might be a suitable method for the assessment of ischaemic liver lesions.