The efficiency of ventilation in 31 poultry houses (16 for layers and 15 for broilers) located at different localities at Behera and Alexandria Governorates was studied. It has been found that the mean values of ambient temerature (°C), relative humidity (%), Ammonia (ppm) carbon dioxide (%) were 25.5+ 5.9; 70.48+ 10.9; 10.3+ 3.03 and 0.08+ 0.02 respec tively. On the other hand, a nearly similar results were obtained in the investigated layers and broiler houses. Such concentrations and values provide an evidence of the efficiency of ventilation which have a good effect upon the comfort of poultry health and production.