Two nitrogen-balance experiments were conducted to determine the optimum balance patte among four amino acids (lysine,methionine,tryptophan and threonine)on a digestible basis in the diet of piglets (10 kg) treated with lipopolysaccharide or saline as control.The method of amino acid deletion was adopted.All pigs were of a single genetic background and geographical origin.In each group,fifteen Landrance×Rongchang castrated piglets were allotted randomly to one of five groups of dietary amino acid regimens.The positive control group was supplemented with four amino acids.One of the four amino acids was reduced by about 25% in the respective treatment groups.After finishing the nitrogen-balance experiments,the slaughter technique was used to determine the ideal amino acid digestibility of the positive control by using chromium oxide (3 g/kg) as the indicator.The results showed that the ideal amino acid patte of lysine/methionine/threonine/tryptopham on the digestible basis was 100:27:29:59 for 10 kg pigs under immune stress,and 100:30:21:61 for piglets under normal conditions.