Bilateral adrenalectomy followed by immediate transplantation of adrenal slices into muscular tissue was performed in 7 patients with Cushing's disease and 1 with bilateral pheochromocytoma. Patients were followed for 1 to 7 years and only 1 had evidence of a functional graft (serum cortisol level at the lower limit of normality). Low levels of dehydroepiandrosterone sulfate, aldosterone and cortisol were found in the remaining patients. Acute stimulation with adrenocorticotropichormone did not increase either cortisol or aldosterone levels in any patient. We conclude that prospective studies are needed to elucidate factors that could improve the success of adrenal implantation, since the literature shows examples of functional grafts, while the majority of the cases are unsuccessful.