Recent economic trends, especially the worldwide decline in oil prices, and an altered political climate in the United States have combined to bring about major reductions in research on renewable energy resources. Yet there is no escaping the "facts of life" with regard to these resources. The days of inexpensive fossil energy are clearly numbered, the credibility of nuclear energy has fallen to a new low, and fusion energy stands decades or more from practical realization. Sooner than we may wish ,we will have to turn to renewable raw materials - plant "biomass" and, especially, wood - as significant suppliers of energy for both industry and everyday needs. It is therefore especially important to have a single, comprehensive and current source of information on a key step in any process for the technological exploitation of woody materials, cellulose hydrolysis. Further­ more, it is essential that any such treatment be unbiased with respect to the two methods - chemical and biochemical - for the breakdown of cellulose to sugars. Researchers on cellulose hydrolysis have frequently been chided by persons from industry, especially those individuals concerned with determining the economic feasibility of various technological alternatives. They tell us that schemes for the utilization of wood and other such resources fly in the face of economic realities.