Transplantation of adrenal cortical tissue may represent an alternative treatment to reestablish glucocorticoid secretion in adrenal insufficiency. In the present work, performed in adrenalectomized rats and adrenalectomized rats with a complete autotransplanted adrenal into the spleen, several hormones and biochemical parameters were measured and compared to control animals, in order to examine hormone interactions. Rats were sacrificed three weeks after surgery, and plasma and tissue samples were obtained for hormone and biochemical measurements. In adrenalectomized animals, plasma corticosterone, aldosterone and insulin levels were profoundly decreased, whereas in autotransplanted rats plasma corticosterone levels showed a partial recovery, aldosterone plasma concentrations remained low, and plasma insulin levels increased to values close to those of the controls. Both groups showed a marked elevation of plasma ACTH levels, as well as significantly increased plasma glucagon concentrations. In autotransplanted animals, most of the biochemical parameters, which were altered in adrenalectomized rats, returned to normal levels. These results suggest that increased glucagon levels in adrenalectomized and autotransplanted animals, may contribute to the marked increase of plasma ACTH, and could also be important in the recovery of plasma glucose and hepatic glycogen observed in autografted rats. Since high glucagon concentrations alone were unable to normalize carbohydrate levels in adrenalectomized animals, it appears that glucagon can act only in the presence of corticosterone.