AbstractPretreatment of moist seeds at certain temperatures can reduce seed dormancy, but such observations represent the net effect of pretreatment. Seeds of Sitka spruce (Picea sitchensis [Bong.] Carr.) were raised to 30% moisture content and pretreated at five different temperatures between 5 and 30°C for up to 24 weeks (168 d). Subsequent ability to germinate at 10°C and viability were then determined in order to investigate the effects of pretreatment on seed dormancy and survival. There was a curvilinear, negative semi-logarithmic relationship between seed longevity and pretreatment temperature, such that Q₁₀ for loss in viability increased from 2.6 between 10 and 20°C to 2.8 between 20 and 30°C. Simple multiplicative models combining cumulative normal frequency distributions for each of loss in viability and loss in dormancy were able to describe the changes in ability to germinate at 10°C, after pretreatment at 5, 10 and 30°C. However, in order to quantify the changes in ability to germinate observed at 10°C after pretreatment at 15°C, it was necessary also to invoke a model of dormancy reimposition, while for the results at 20°C it was necessary to postulate both dormancy reimposition and the further loss of this reimposed dormancy. It is concluded that moist seeds of Sitka spruce held at 15 and 20°C cycle between the dormant and non-dormant condition.