Supplementing a 15% protein diet for chickens, with all the protein coming from canola meal, with essential amino acids (EAA) to bring diet levels up to those recommended by NRC, failed to improve weight gain over that of an unsupplemented canola meal diet. While feed:gain ratio of the EAA-supplemented diet was improved, performance was markedly inferior to that of a 20% protein corn-soybean meal diet. Supplementing the canola meal basal diet with corn oil, lysine, or lysine plus arginine resulted in significant responses; however, performance was again far below that of the corn-soybean meal positive control diet. Supplementing the canola meal basal with EAA to bring levels up to close to the corn-soybean meal control diet resulted in performance which was superior to that obtained in the experiments in which EAA were supplemented to NRC requirement levels. However, performance was still markedly inferior to the corn-soybean meal control diet. A point of interest was the failure to demonstrate a need for methionine supplementation of the canola meal diet, even though by calculations it should have been deficient in this amino acid. A marked improvement in performance occurred when the level of methionine supplementation was reduced from 0.28 to 0.1% for the canola meal diet, supplemented with lysine, arginine and tryptophan. This clearly demonstrates that excess methionine or sulphur supplementation can markedly alter the performance of canola meal diets and may be one of the major reasons why EAA supplementation of semipurified diets that contain canola meal has failed to result in marked improvements in performance. Key words: Canola meal, amino acid supplementation, chickens