The study was carried out at the experimental station, Faculty of Agriculture. Damascus University. 1464 of the hybrid Lohman broiler chicks, one day old, were divided randomly and equally into 8 groups (182 chicks/ G) with 3 replicates of 61 chicks each. Chicks in each replicate were reared separately on deep litter in an independent room of open housing till the age of 42 days. All housing and management procedures were similar for all chicks while the feeding was different throughout the fattening period in terms of the amounts of lysine and methionine added to the mix feed. Chicks of G1, G2, G3 and G4 were fed on plants mixtures supplemented with 1, 1.5, 2 and 2.5 kg/ ton of methionine, respectively. Chicks in G5, G6, G7 and G8 were fed on the same mixtures of the previous groups but supplemented additionally with 1kg/ton of lysine. Result showed that adding lysine 1kg/ton and methionine 2kg/ton to plant mixtures of feeds of broiler helped in improving significantly most of the indicators of productivity and this in turn led to a reduction of the cost of feeding and to produce 1 kg live weight, thereby raising the index profit from the process of fattening and increasing the gain from fattening process.