Termination of larval diapause in the tufted apple budmoth,Platynota idaeusalis(Walker), is a dynamic process in which insect development is influenced by both the nature and the timing of the various stimuli to which it is exposed. Parameters investigated in this study with respect to diapause termination included time of inoculation (egg hatch) in the field, temperature, and photoperiod. Each factor was shown to affect significantly diapause development in diapausing larvae. However, the magnitude of the effect of each consistently diminished as the season progressed. Comparisons of laboratory and field strains ofP. idaeusalis, reared under similar conditions, showed no significant differences in their respective diapause responses to each of the factors investigated. Larvae inoculated out of doors earlier in autumn exhibited a less intense diapause than those inoculated later. Diapause termination was accelerated when larvae were exposed to higher constant temperatures and longer stationary daylengths, or both. Because natural temperatures rarely rise above 27°C (the optimum temperature tested for diapause termination) between November and March in North Carolina, larval diapause inP. idaeusalisis most likely terminated by increasing daylengths in the spring, with temperature acting as a modifying influence in the overall rate of diapause development.