To study the prevalence of ALV antigen in different poultry flocks in Upper Egypt, serum and egg samples were collected from poultry farms representing different ages, different raising systems and different chicken types including table egg layers, meat type broilers, breeders and random native breeds. Samples were tested for detection of P.27 Common antigen of ALV by ELISA test. All chickens flocks possessed ALV antigen at various degrees. The highest percentage was detected in meat type chicken flocks and balady chickens. Titre of endogenous virus was greater than exogenous virus.