The time course of changes in glycemia, insulinemia, corticosteronemia, liver glycogen, food intake, body and stomach's fresh weight were studied in rats subjected to electrolytic bilateral destruction of the ventromedial hypothalamus (VMH) and in a sham-operated (SO) group. Some of these parameters were determined during the first four hours after lesioning and all were measured also up to two weeks. Glycemia increased steadily, attaining 37.1% 120 min post-lesioning, and a parallel decrease (51.3%) in hepatic glycogen was observed. Twenty minutes after VMH destruction the insulin levels were 215.8% higher than in the SO group, a difference that was reversed 220 min later. At the first day post-lesioning the insulin levels increased 348%. It is suggested that the release was stimulated by the early reflex insulin secretion elicited by food ingestion. During the first hours after VMH lesioning corticosteronemia was elevated to 253.9% of the corresponding parameter in the SO group. When the effects of the lesion were followed up during fifteen days it was found that glycemia and hepatic glycogen returned to normal levels but insulinemia went up again. Plasma insulin increased 325.9% by the end of the observation period while corticosteronemia was 404.5% higher as compared with the SO animals. Food intake increased 63.5% on the day after lesioning and continued to rise, attaining 106% by the fifteenth day, which paralleled the weight gain (31%). A close topographic correlation was found in this study between the precise lesioning of the ventromedial nuclei of the hypothalamus and the changes herein described.