The present work was conducted to study the relationship between developmental stages of Pectinophora gossypiella (Saund.) and required thermal units at two constant temperatures, 25 and 30°C ± 1°C in Sharkia, Dakahlia, Monofia and Gharbia Governorates, in Delta, Egypt. Results showed that there was variation in growth periods that is necessary to complete the various developmental stages of pink bollworm from eggs to adult, whether, on 25 or 30°C, at the four Governorates. Increasing the temperature was accelerated the developmental rate and shortened the periods of the different stages. Also, the lower thermal threshold for the development of pink bollworm stages differed from governorate to another. In the four Governorates, Sharkia, Dakahlia, Monofia and Gharbia, at the generation, t0's were 12.92, 11.67, 11.99 and 11.23°C (the coefficient of variability was 7.089) and the DDU were 541.67, 586.67, 536.18 and 564.69 units (the coefficient of variability was 0.86), respectively. The biological