The effects of chronic ethanol intake were studied on the morphology of rat hippocampal granule cells. Sprague-Dawley rats were exposed to ethanol in a liquid diet for 5 months followed by a 3 week withdrawal period. A control group was fed similar amounts of the same diet but with ethanol replaced by maltose-dextrins. Intracellular recordings were performed using the hippocampal slice preparation and the granule cells from animals of both groups were injected with HRP. The ethanol treatment produced a significant increase in the average length of the dendrites of granule cells compared to the control group. Chronic ethanol intake produced a decrease in the number of dendrites in the proximal region of the tree (80-180 microns) but also a significant increase in the number of dendrites in the distal portion (260-340 microns). The decrease in the number of proximal dendrites suggests that ethanol could be affecting a population of neurons with afferent inputs in the proximal region of the tree or that ethanol could interfere with the normal maturation processes of the granule cells. The increase in the number of dendrites in the distal region of the tree suggests, however, an accelerated growth or sprouting of dendrites in the molecular layer.