Several factors are involved in the persistence of endocrine alterations after renal transplantation, among which the following are to be mentioned: (1) duration of chronic uraemia before renal transplantation; (2) residual function of the patients' native kidneys; (3) quality of function of the renal graft; (4) modulation of secretion, transport, and degradation of hormones, and/or (5) altered target organ responsiveness to hormones induced by immunosuppressive drugs (glucocorticoids, azathioprine, cyclosporin A) or altered internal environment. In kidney transplant patients the following endocrine abnormalities are to be mentioned: dissociation of the physiological relationship between aldosterone synthesis and function of the renin-angiotensin system, abnormal volumetric regulation of arginine vasopressin secretion, suppressed responsiveness of cortisol secretion to stimulatory manoeuvres, persistent secondary hyperparathyroidism, relative deficiency of insulin (induced by glucocorticoid therapy), with consequent carbohydrate intolerance or even diabetes mellitus, suppressed response of gastrin and pancreatic hormone secretion to a test meal, and reduced responsiveness of atrial natriuretic peptide secretion to central hypervolaemia. Episodes of acute graft rejection are characterized by endocrine alterations similar to those seen in patients with acute or chronic renal failure.