Divergent pattern in pyruvate efflux from livers perfused with As2O3 and livers of animals previously repeatedly treated with the toxicant was observed in earlier experiments (Reichl et al. 1987, 1988). Further studies of the effect of As2O3 on carbohydrate metabolism were therefore performed. Male guinea pigs received either a single dose of As2O3 10 mg.kg-1 s.c. or repeated doses of 2.5 mg.kg-1 bis in die (b.i.d.) on 5 consecutive days. One hour after the single dose or 1 h and 16 h after the last injection in the repeated treatment group the animals were sacrificed under anaesthesia. The livers were removed by a freeze-stop technique and the contents of glycogen and glycolysis intermediates were measured. In the single dose group a decrease in fructose-1,6-diphosphate and glycerol-aldehyde-3-phosphate and an increase in phosphoenol-pyruvate and pyruvate was observed. In the repeat dose, 1-h group a significant decrease in glycogen, glucose-6-phosphate, fructose-6-phosphate, glycerolaldehyde-3-phosphate, dihydroxyacetonephosphate, 2-phosphoglycerate and pyruvate was found. In the repeat dose, 16-h group the contents of glycogen, glucose-6-phosphate, pyruvate and lactate were diminished. The most prominent finding after repeated As2O3 administration was a marked depletion in total carbohydrate content. This was due mainly to depletion of glycogen.