The aim of the present study was to determine whether dietary peptide concentration had an effect on endogenous ileal amino acid flow in the growing pig. Eight 33 kg live weight entire male pigs had post-valve T-caecum (PVTC) cannulas surgically implanted for the collection of ileal digesta. The pigs were fed twice daily at 100 g/kg metabolic body weight per d and were given diets containing enzyme-hydrolysed casein (EHC) at 0, 50, 100 and 200 g/kg in a Latin-square design. A basal casein-based diet was fed to the pigs for 6 d periods between receiving the experimental diets. The pigs received the experimental diets for 8 d periods, with continuous collection of digesta for 24 h on each of the fifth and eighth days. The endogenous ileal amino acid flows were determined with reference to recovery of the marker, Cr, directly for pigs receiving the protein-free diet or after centrifugation and ultrafiltration (10 000 Da molecular mass cut-off) for pigs on the EHC-based diets. Mean endogenous ileal N flows were 1753, 1948, 2851 and 5743 μg/g DM intake when the pigs received diets containing 0, 50, 100 and 200 g EHC/kg respectively. There was a significant (P < 0·05) effect of dietary peptide concentration on the endogenous ileal flows of N and all of the amino acids, with an increase in endogenous ileal amino flow with increasing dietary EHC concentration.