The developmental time, survivorship and reproduction of Aphis gossypii Glover was evaluated on detached cucumber leaves at nine constant temperatures ranging from 15 +/- 1 degrees C to 35 +/- 1 degrees C in 2.5 degrees C increments in the laboratory. Developmental periods of immature stages ranged from 10.8 days at 15 degrees C to 4.1 days at 30 degrees C and 32.5 degrees C. Constant 35 degrees C was lethal to immature stages of A. gossypii. The lower developmental threshold for the cotton aphid was estimated at 6.0 degrees C and it required 92.6 degree-day development for a first instar to become adult. The average reproduction rate was 82.1 nymphs female(-1) at 25 degrees C and 2.3 nymphs female(-1) at 32.5 degrees C. The mean generation time of the population ranged from 6.8 days at 32.5 degrees C to 22.8 days at 15 degrees C. The highest per capita growth rate (r(m) = 0.526) occurred at 25 degrees C and the lowest at 15 degrees C (r(m) = 0.208) and 32.5 degrees C (r(m)=0.132). It was evident that temperatures over 30 degrees C prolonged development, increased mortality of immature stages, shortened adult longevity and reduced fecundity. The optimal range of temperature for population growth of A. gossypii on cucumber was very broad and ranged between 22.5 degrees C and 30 degrees C.