The developmental rime, survival and reproduction of the cotton aphid, Aphis gossypii Glover (Hom., Aphididae). were evaluated on detached cotton leaves at five constant and two alternating temperatures (15. 20. 25, 30, 35, 25/30, and 30/35 degrees C). The developmental periods of the immature stages ranged from 12.0 days at 15 degrees C to 4.5 days at 30 degrees C, A constant temperature of 35 degrees C was lethal to the immature stages of A. gossypii. The lower developmental threshold for the cotton aphid was estimated at 6.2 degrees C and it required 108.9 degree-days for a first instar to become adult. The average longevity of adult females was reduced from 39.7 days at 15 degrees C to 12.6 days at 30/35 degrees C. The average reproduction rate per female was 51.5 at 25/30 degrees C and 20.9 at 30/35 degrees C. Mean generation time of the population ranged from 10.4 days at 30 degrees C to 24.5 days at 15 degrees C. The largest per capita growth rate (r(m) = 0.413) occurred at 30 degrees C, the smallest at 15 degrees C (r(m) = 0.177). It was evident that temperatures over 30 degrees C prolonged development, increased the mortality of the immature stages, shortened adult longevity, and reduced fecundity. The optimal range of temperature for population growth of A. gossypii on cotton was 25/30-30 degrees C.