The effects of the presence of males onfemales aggressiveness and feather picking were investigated in two groups, the first one was single-sexed group (140 femal es), the other group was mixed (10 males and 130 females), both groups were reared on deep litter systemfor layers of Leghorn breed . The obtained results revealed that, aggressive behaviour (aggressive peclcs, threats and fights ) among females was significantl y less frequent in groups that included males (mixed group}. Agonistic behaviour among females was 62% more frequent : in single-sexed group, than among layers in mixed group. The males were seldom seen to show aggressive behaviour toward s female or toward s each other. Regarding feather peclcs , there were no significant differences between single-sexed and mixed groups. from this stud y it could be concl.uded that the presence of males had a reducing ef fect on agonistic behaviour, but not on feather pecking among female laying hens housed in large groups at high stocking density. Al so the presence of males is very important for getting high fertility percentage in layers prod ucing eggs used in hatching process. On opposite direction, the presence of males have no importance in layers producing eggs used for human consumption