The acute metabolic effects of recombinant human insulin-like growth factor-1 (rhIGF-1) were studied after an overnight fast in six maintenance hemodialysis (MHD) patients, six chronic peritoneal dialysis (PD) patients and six normal subjects. Each subject received a subcutaneous injection of rhIGF-1, 50 or 100 micrograms/kg body wt, given in random order on two occasions separated by 7 to 21 days. After the rhIGF-1 injection, plasma insulin, C-peptide, cortisol, amino acids and glucose decreased. The magnitude of the decrease was greater with the larger rhIGF-1 dose. The fall in plasma insulin, C-peptide and many amino acid concentrations was less and the decrease in glucose was similar in the MHD and CAPD patients as compared to normals. With 50 micrograms rhIGF-1/kg, plasma insulin and C-peptide decreased more quickly and often to a greater magnitude in normal individuals. With 100 micrograms rhIGF-1/kg, the decrease in plasma insulin, C-peptide and amino acids in the MHD and CAPD patients was almost as frequent as in the normal subjects, but the magnitude of the fall was often significantly less. This impaired response occurred in both MHD and CAPD patients even though, with the 100 micrograms rhIGF-1/kg dose, their plasma IGF-1 was significantly higher than in normals during most of the first four hours after injection. These results provide the first in vivo evidence for resistance to the metabolic effects of rhIGF-1 in patients with advanced renal failure.