Dystrophic mice were investigated with regard to their regulation of blood glucose and insulin secretion in vivo. The following were also measured: tissue glycogen levels, activity of the glycogenolytic hydrolase, acid amyloglucosidase, and in vitro glucose utilization by liver, muscle and adipose tissue. Basal levels of blood glucose and plasma insulin of dystrophic mice were essentially within the same range as in the clinically unaffected littermate controls. Dystrophic mice had a decreased tolerance to glucose and glibenclamide; the secretion of insulin in response to these secretagogues was moderately reduced. Insulin release following beta-adrenergic stimulation, however, was increased in the dystrophic mice. Glycogen levels and acid amyloglucosidase activity were increased in dystrophic muscles but were normal in liver. Acid amyloglucosidase activity in pancreatic islets was lower in the dystrophic mouse. Glucose utilization in vitro appeared normal in liver tissue from dystrophic mice; in dystrophic muscle there was a threefold increase in 14CO2-production with no concomitant increase in either glycogen or 14C-incorporation into glycogen. 14CO2 production and 14C-incorporation into lipid and glycogen were increased in dystrophic adipose tissue. We suggest that the decreased glucose tolerance, and the reduced insulin response to glucose in the dystrophic mouse are compensated by an increased glucose utilization in muscle and adipose tissue and an increased beta-adrenergic-mediated secretion of insulin.