Development rates of the egg, larval and pupal stages of codling moth, Cydia pomonella (Linnaeus), on apples were determined at constant temperatures of 15, 17, 20, 25 and 30 ± 1 °C and at fluctuating temperatures. There was a linear relationship between rate of development and temperature over the range of temperatures used. The lower threshold temperatures for embryonic, larval and pupal development were 11.1, 7.9 and 9.9 °C, respectively. The degree-days required to complete embryonic, larval and pupal development were 80.1, 345.5 and 280.0, respectively. The responses of the different stages of C. pomonella to constant temperatures were similar to those under fluctuating temperatures. It is suggested that a base temperature of 10 °C be used in South Africa for calculating degree-days in predicting phenological events such as first egg hatch.