The present study was carried out at the Department of AnimalWealth Development, faculty of Veterinary Medicine, Zagazig University The aim was to study the genetic resistance to Newcastle disease and Fowlcholera among purebred Lohman Selected Leghom (LSL) and, Fayoumi(FF). This study revealed the following main points: Fayoumi cockerels had significantly higher fertility percentage compared with those of Lohman Selected Leghom (LSL) (88.70 vs.81.33 %). Non-significant differences for hatchability percentage were found among purebred, crossbred and reciprocal crossbreds. In additionnegative heterosis was estimated for crossbred and reciprocal15th day post drug treatment.The highest concentration of amoxycillin was detected in liver thankidney and muscles. Amoxycillin residues disappeared on the 7th day post drug treatment from muscles and disappeared on the 9th day from bothliver and kidney post drug treatment.-128~