This study examines the potential role of the neuropeptide, galanin, in stress‐induced inhibition of insulin secretion in swimming mice. Firstly, the pancreatic and adrenal content of galanin‐like immunoreactivity was determined in mice after swimming stress. It was found that pancreatic content was significantly lower in stressed mice than in resting controls, both after 2 (P < 0.05) and 6 (P < 0.025) minutes of swimming, suggesting partial release of pancreatic galanin during stress. In contrast, the adrenal content of galanin‐like immunoreactivity did not change during the swimming stress. Gel filtration of tissue extracts indicated that (1) mouse pancreas contains two forms of galanin‐like immunoreactivity; one co‐eluting with synthetic porcine galanin (centred on K_av of 0.70) and another with a larger molecular weight (centred on K_av, of 0.30), and (2) mouse adrenal contains a small void volume‐peak and a larger peak of immunoreactivity, the latter co‐eluting with synthetic galanin. Secondly, the effects of swimming stress on plasma glucose and insulin levels were compared in mice that received high titre rabbit anti‐galanin serum with those in mice receiving normal rabbit serum. In normal rabbit serum‐pretreated swimming mice, glucose‐induced insulin levels were only 50% of resting controls (P < 0.01). Immunoneutralization of galanin with specific antiserum abolished this swimming stress‐induced inhibition of glucose‐stimulated insulin levels. This was accompanied by a modestly enhanced rate of glucose disappearance. These findings suggest that pancreatic galanin is released during swimming stress in mice and that endogenous galanin makes a major contribution to stress‐induced impairment of insulin secretion.