Five barrows with an average initial BW of 45 kg and fitted with a T-cannula at the distal ileum were fed 5 diets to determine the standardized ileal digestibility (SID) of AA in corn (Zea mays) distillers' dried grains (DDG), DDG with solubles (DDGS), high-protein DDG (HPDDG) and high-protein DDGS (HPDDGS). On a DM basis, the test ingredients contained 33.7% CP, 19.2% ADF, and 53.1% NDF for DDG; 30.3% CP, 11.8% ADF, and 40.6% NDF for DDGS; 62.5% CP, 28.4% ADF, and 45.1% NDF for HPDDG; and 52.4% CP, 17.4% ADF, and 30.4% NDF for HPDDGS. The 5 diets consisted of a N-free diet (NFD) and 4 semipurified diets, in which the test ingredient was the sole protein source with chromic oxide added at 5 g/kg as an indigestible marker, and fed for each of 5 periods. The NFD was used to determine basal endogenous AA losses. Each period consisted of a 5-d adjustment period and 2 d of ileal digesta collection for 10 h on each of day 6 and day 7. Amino acids in the test ingredients were well digested by pigs and SID of Lys for DDG, DDGS, HPDDG, and HPDDGS were 88.6, 79.9, 94.6, and 85.8%, respectively. Corresponding values for were Met 93.9, 92.8, 97.1, and 94.6%. The SID of Lys was greater (P < 0.05) in HPDDG than DDGS. In general, digestibility of AA in the high-protein coproduct of the dry grind processing of corn into ethanol was 2 to 8 percentage units more than in the regular coproduct and 2 to 9 percentage units less in the coproduct with added solubles.