Six healthy volunteers showed significantly higher plasma islet amyloid polypeptide levels following an oral glucose tolerance test compared to fasting levels. The urine IAPP concentration before and after the OGTT was comparable to that in plasma. Reverse phase HPLC and radioimmunoassay analysis of urine samples revealed a single IAPP-immunoreactive peak. Before hemodialysis, the plasma levels of IAPP and C-peptide, but not of insulin, were significantly elevated in eight fasting patients with chronic renal failure, compared to eight healthy matched control subjects. After hemodialysis, there was a tendency for decreased IAPP levels compared to before dialysis. In summary, elevated levels of plasma IAPP were found in patients with chronic renal failure and the peptide is eliminated by hemodialysis. Furthermore, immunoreactive IAPP is normally present in the urine. These results suggest that IAPP is, at least in part, renally eliminated from the plasma by excretion (glomerular filtration and/or tubular secretion.