Methodological studies on the histochemical technique for the demonstration of G6Pase activity showed that the occurrence of common artifacts: morphological destruction, extracellular precipitation of reaction product and nuclear staining are dependent on the concentration of lead nitrate, buffer and substrate. By studying the effects of systematic variation of the incubation media on the histochemical reaction optimal concentrations of either of these components were determined. An improved medium containing 3.6 mM lead nitrate, 40 mM tris-maleate buffer, pH 6.5, 10 mM G6P and 300 mM sucrose was used for the study of G6Pase distribution patterns in liver acini of juvenile and adult rats of both sexes and in those of starved adult female rats. The results obtained indicate sex dependent differences in the functional organization of the liver acinus and furthermore demonstrate the rapid functional adaptability of liver parenchyma to changes of the nutritional situation.