Evaluation was made of the extent to which amino acids in maize, wheat and barley meals were digested by pigs.Apparent Digestibility (AD) of an individual amino acid was determined as the difference between amino acid intake and amino acid in the ileal digesta, expressed as a percentage of the intake. AD was adjusted to True Digestibility (TD) by correcting for the endogenous amino acid in the digesta, measured after feeding protein-free diets. An attempt was made to account for the possible influence of dietary fibre on digestility determinations by using protein-free diets which provided similar intakes of crude fibre as that achieved with the cereals.4 littermate male pigs (22 kg live weight) were each surgically modified to create an ileo-rectal anastomosis. The large intestine was sealed at both ends and a cannula exteriorized from its lumen to enable fermenting residues to escape. Pigs were housed in individual metabolism crates. Digesta by-passed the large intestine, were expelled via the anus and collected in trays. The spurious influence of bacteria in the large intestine, on digestibility measurement, was thus avoided.