Cortisol and ACTH secretion was studied in 52 healthy subjects who were fasted or fed various diets: standard, high fat, high carbohydrate, high protein. Subjects fed the high protein diet (4gm/kg body weight) showed significant increases in cortisol both at 30 and 60 min after the 1200 hr meal and 30 min after the 1600 hr meal. Increases in cortisol, of a smaller magnitude, were also seen after both the 1200 and 1600 hr meals in each of the diets with 1 gm protein/kg body weight (standard, high fat, high carbohydrate). ACTH was significantly increased following the 1200 hr and 1600 hr meals with the high protein diet. We conclude that dietary protein plays an important role in meal stimulated cortisol release.