Cellular hypersensitivity to an extract of human pancreas, using the leucocyte migration test (LMT), was found in twenty-nine of 101 diabetic and eight of fifty normal control subjects. However, the difference in response between diabetics and controls was confined to young insulin-dependent patients, there being no distinction between normal subjects and older diabetics treated by diet or oral hypoglycemic agents. The use of rat liver mitochondria and bovine insulin as antigens in the LMT did not induce inhibition of leucocyte migration in diabetics or controls.