After the ventral medial hypothalamus of mice was lesioned with gold thioglucose, the dose of insulin required to produce convulsions in 50 percent of the animals was doubled compared to that in nonlesionad controls. No dose of insulin, up to 50 milliunits per gram, produced convulsions in more than 60 percent of the lesioned mice, even though blood glucose levels fell to approximately 24 milligram percent.