Isolated islets of Langerhans of the rat were used to study the effect of starvation on pancreatic insulin and glucagon release. The collagenase method was used to isolate islets from fed and 3-day fasted rats and the hormone release during incubation in various glucose concentrations was compared. After starvation the release of both immunoreactive insulin (IRI) and immunoreactive glucagon (IRG) was impaired. Starvation also resulted in decreased circulating IRI and glucose levels but circulating IRG levels were not changed. The total extractable IRI and IRG content of the pancreas was not affected by starvation.