Technical Abstract: Xylose production using corncobs is an established industrial practice. The cellulose-rich xylose-extracted corncob residue (X-ER), as a byproduct, is a potential energy resource. Efforts to convert the cellulose fraction of X-ER to ethanol have been unsatisfactory due to a lack of understanding of the substrate characteristics. The present study characterized X-ER for its potential utilization in conjunction with the sequential production of xylose and cellulosic ethanol. We found the current dilute acid treatment procedures used for the corncobs by the xylose-production industry were insufficient for deconstruction of corncob cellulose structure in order to release available sugars for the subsequent cellulosic ethanol conversion. After a secondary dilute acid hydrolysis of the X-ER, an additional 30% hemicellulose was recovered. In addition, a more efficient enzymatic hydrolysis of X-ER was observed resulting in a significantly higher yield of glucose conversion compared with an untreated X-ER control. These results suggest X-ER can be utilized for cellulosic ethanol production; however, the current industry processed X-ER is not ready for immediate applications of economic ethanol conversion. Based on the results of the current research, it is possible to pursue a combined production of xylose and cellulosic ethanol from corncobs and its byproduct X-ER using improved corncob pretreatment procedures and fermentation strategies.