The in vitro perfusion of the isolated rat pancreas as described by Anderson and Long (1947), Ross (1972), Grodsky and coworkers (1983, 1984), and Muñoz and coworkers (1995) offers the advantage to study the influence of carbohydrates, hormones, and drugs such as sulfonylureas not only on insulin but also on glucagon and somatostatin secretion without interference of secondary effects resulting from changes in hepatic, pituitary, or adrenal functions.