The paper summarizes and evaluates data on estimates for the amount and amino acid (AA) composition of basal endogenous crude protein (CP) at the terminal ileum of pigs derived from 33 ileal digestibility studies with pigs (30-100kg BW). Different methods and approaches are used to obtain these estimates: (A) the N-free diet method (16 studies), (B) calculations based on ileal digestibility values of diets with highly digestible protein sources (casein or wheat gluten) (11 studies), (C) the regression method (3 studies), (D) the enzymatic hydrolyzed casein (EHC) method (2 studies) and (E) the N-free diet method with intravenous infusion of AAs (1 study).The mean values for the flow of basal endogenous ileal CP (6.25x N) for the five respective methods were 10.5, 12.6, 12.0, 17.1 and 12.7g/kg dry matter (DM) intake. The overall mean value using all observations was 11.8g/kg DM intake. The mean AA composition of basal endogenous protein (g/16gN) was estimated as 3.2 for isoleucine, 4.2 for leucine, 3.4 for lysine, 1.0 for methionine, 1.8 for cystine, 2.9 for phenylalanine, 2.6 for tyrosine, 5.1 for threonine, 1.2 for tryptophan, 4.5 for valine, 3.4 for arginine and 1.6 for histidine.The flow of basal endogenous ileal CP and AAs can be considered as an inevitable loss for the pig. Data on the flow of basal endogenous protein and AAs can be used to calculate true or standardized ileal digestibility values or corrected apparent ileal digestibility values of feed ingredients for pigs. The use of more accurate and additive ileal digestibility values of AAs in feed ingredients improves diet formulation for pigs, in which AA supply via the diet is matched with AA requirements.