The present study was carried out at Mahala, Basion and Tanta districts in Gharbia Governorate during 2006 &2007 cotton seasons to study prediction of ِِِِِِamerican bollworm, Helicoverpa armigera (Hüb.), depended on accumulated heat units in cotton fields with enough period for the pest control. The host plants of H. armigera surveyed in investigation areas during the wintry, summery and niley seasons. Results indicated that, seasonal abundance appeared in four main peaks of the capture that occurred during the two investigation seasons, at the three districts. The monthly average number of catches ranged between 2.86 to 11.16 male /Trap/month at three districts during the tested seasons. Tanta had the largest significant mean number of the capture for months followed by Mahala and Bason. Fit polynomial regression equation between the two variables that was represented in coefficient of determination R² values indicated that the equation degree14 for the three districts. The R² values ranged at three districts between 0.64731 and 0.94397. Sum of deviations   square for the expected from observed population ranged  between 12.31 and 45.08 at Mahala,  15.99 and 98.99 at Basion  and at Tanta the population take the same trend for the two seasons. Therefore, accumulated heat units can be used to forecast H. armigera population before appearance with a month using equation Y=a +b₁x +……b₁₄x¹⁴ under the same field condition of host plants at the three different districts in Gharbia Governorate.