Abstract 1. 1. Analyses of inorganic phosphate, adenosine triphosphate, phosphocreatine, glycogen, lactate and pyruvate were determined on cardiac muscle, skeletal muscle and liver samples from thirteen-lined ground squirrels, Citellus tridecemlineatus. 2. 2. Comparison was made between animals maintained in the laboratory and three groups of field animals: Group M, captured in May and sacrificed 1 week later; Group N, captured in May and sacrificed 3 months later in August; and Group O, captured in September and sacrificed 1 week later. 3. 3. When these data are compared with data derived from control squirrels it is seen that, in general, total high-energy phosphates and glycogen decreased while inorganic phosphate, lactate and pyruvate increased in the field groups. 4. 4. It is concluded from the data obtained from Group M that the metabolic events associated with awakening from hibernation in the laboratory simulate those associated with awakening in the field. An additional factor of stress may be operable in Group N while the metabolic status of Group O approximates that of controls.