The seasonal fluctuation of the American bollworm (ABW), Helicoverpa armigera (Hub.), (moths and larvae) was studied on cotton, Gossypium barbadense and okra, Hibiscus esculentus, in Dakahlia Governorate during 2007 and 2008 cotton seasons. Results revealed that the population of ABW male moths occurring three peaks each season. The first peak had highest average number of male moths than others during the two seasons. Populations of ABW larvae infest cotton and okra plants appeared two peaks during the same period. The average numbers of larvae on okra was higher than cotton during the two seasons and average. The probability regression values revealed highly significant between accumulated heat units and each of ABW male moths and larval infestation in cotton and okra. The calculated R^2 values ranged between 0.8148 and 0.9619. The same trend was found between accumulated ABW male moths and larval infestation in cotton and okra. The calculated R^2 values ranged between 0.9185 and 0.9793. Also, between larval infestation in okra and cotton plants were highly significant. The calculated R^2 values ranged between 0.6030 and 0.9899. Consequently, accumulated heat units can be used to predict pheromone traps catch and larval infestation on okra and cotton. Pheromone traps catch can be used to predict larval infestation on okra and cotton also can be used larval infestation on okra to predict larval infestation on cotton.