Cholesterol in chicken brain has been determined after head irradiation with 60Co gamma rays. The brain of five-week-old white Leghorn chickens, irradiated with 1200 R showed appreciable decrease in its cholesterol content after two and five days, and a slight increase after seven days of irradiation. But the cholesterol content after seven days of irradiation was still less than the control values. However, an insignificant increase in brain cholesterol (than control) was observed after 14 days of irradiation. Nine to ten weeks old Rhode Island Red chickens exposed to 4000 R head gamma-irradiation exhibited a similar effect in cholesterol content of the brain.