The effects of temperature on dormancy loss, germination and viability were investigated in seeds of Aesculus hippocastanum L. harvested over a 4-year period. Release from embryo dormancy in freshly harvested seeds was manifest in two phases of morphological growth: initially, when the seed lot was only partially released, axis emergence resulted primarily from cotyledonary petiole extension without radicle extension; subsequently, when the seed lot was totally released, axis emergence of all seeds was followed immediately by extension to >1 cm through growth of the radicle. Germination (axis emergence and radicle extension) at 16°C was a function of pre-treatment period at 2–11°C. The rate of dormancy loss (probit germination d−1) increased linearly below a ceiling temperature for the chilling response; this temperature was estimated to vary from 13°C to 16°C for two seed lots harvested in separate years. Dormancy periods for individual seeds within both seed lot populations can be described by cumulative normal distributions; the predicted standard deviation of chilling units below the ceiling temperature (i.e. thermal time) was 186°C d. Visible germination occurred during the process of stratification at 2°C, starting after 21–25 weeks. By contrast, three years of hy-drated seed storage at 16°C, which was a non-permissive temperature for dormancy loss, resulted in little pre-emergence of the axis during stratification; approximately one third of the seeds remained germinable. The implications of these quantitative analyses of the physiological processes in recalcitrant seeds for the development of improved storage methods are discussed.