Technical Abstract: Some of the world's most productive soils lie within cold regions. To enhance the productivity and quality of soil resources within these regions, knowledge must be advanced concerning the impact of freezing and thawing on soil properties and processes. The International Symposium on Physics, Chemistry, and Ecology of Seasonally Frozen Soils is a step toward broadening our knowledge of frozen soil processes. This paper emphasizes the physical nature of frozen soil and the importance of freezing and thawing to the transport of water and heat at the earth's surface. We also discuss the chemistry and biology of the soil system as affected by freezing and thawing. Ascertaining changes in ecosystem structure and productivity in response to perturbations in climate or management depends primarily on the use of models; these models require the acquisition of new knowledge to better define linkages among the physical, chemical, and biological components in cold regions. New knowledge concerning the dynamics of the frozen soil system will allow global societies and industries to develop sustainable and environmentally-safe management systems.