A map of ecoregions of Alaska has been produced as a framework for organizing and interpreting environmental data for state, national, and international inventory, monitoring, and research efforts. The map and descriptions for 20 ecological regions were derived by synthesizing information on the geographic distribution of environmental factors such as climate, terrain including information of physiography, geology, glaciation, permafrost, and hydrologic features, soils and vegetation. A qualitative assessment was used to interpret the distributional patterns and relative importance of these factors for influencing the character of the landscape from place to place. The specific procedures and materials used to delineate the ecoregion boundaries are documented and a description of the enviornmental characteristics that occur in each resultant ecoregion is provided.