In 24 patients with a kidney transplant and in 10 healthy subjects the test meal response of immunoreactive insulin (IRI), glucagon (IR-G), pancreatic polypeptide (IR-PP) and gastrin (IR-Ga) was studied. Patients with a kidney transplant showed significantly elevated basal plasma glucagon levels but normal levels of plasma IRI, IR-PP and IR-Ga. After administration of a test meal a significantly suppressed response of IRI, IR-PP and IR-Ga secretion was observed both in the patients treated with azathioprine as well as those treated with ciclosporin. In patients of the ciclosporin group the compromised response of IR-Ga and IRI secretion was significantly more marked than in subjects in the azathioprine group. From the results obtained in this paper it follows that the type of immunosuppressive drugs (azathioprine or ciclosporin) seems to be of minor importance in the pathogenesis of the described endocrine abnormalities.