sugarcane bagasse and wheat straw were subjected to alkali treatment at 200 $degree$ c for 5 min and at 3. 45 mpa gas pressure (steam and nitrogen), followed by an explosive discharge through a defibrating nozzle, in an attempt to improve the rate and extent of digestibility. the treatment resulted in the solubilization of 40-45 of the components and in the production of a pulp that gave saccharification yields of 80 and 65 in 8 h for bagasse and wheat straw, respectively. an analysis of the alkali-exploded products showed that substantial amounts of hemicellulose and a small proportion of the lignin were solubilized. the percentage crystallinity of the cellulose did not alter in either substrate but there was a substantial reduction in the degree of polymerization the superiority of the alkali-explosion pretreatment is attributed to the efficacy of fiber separation and disintegration; this increases the surface area and reduces the degree of polymerization. (edited author abstract) 33 refs