The effects of starvation on the tissue concentrations of some peptides common to the gastrointestinal tract and the central nervous system have been examined. Groups of 6 rats were either fed ad libitum or starved for up to 4 days and killed by decapitation. Antrum, fundus, duodenum, jejunum, ileum, colon, pancreas and brain were dissected, weighed and then frozen on dry ice. The tissues were extracted sequentially in boiling water and 3% acetic acid, centrifuged and the supernatants radioimmunoassayed for gastrin, cholecystokinin (CCK), vasoactive intestinal peptide (VIP), gastric inhibitory peptide (GIP) and somatostatin. Each peptide was not assayed in each tissue. Starvation had no effect on the concentrations of peptides measured in the fundus (somatostatin and VIP), ileum (somatostatin, GIP, VIP) and colon (somatostatin, GIP, VIP). VIP concentration was increased in the jejunum and GIP was increased in both the duodenum and jejunum. Antral gastrin was the only peptide in the gastrointestinal tract to be decreased by food deprivation. Somatostatin concentration was approximately doubled in the antrum, duodenum, jejunum and pancreas. Brain VIP was unchanged. Brain somatostatin and CCK were significantly reduced by starvation. We conclude that starvation results in organ-specific and hormone-specific alterations in tissue concentrations of peptides of the gastrointestinal tract and the central nervous system.