The use of agricultural wastes for energy and intermediary chemicals has economic, ecological and strategic interest. The strong hydrolysis of the lignocellulose residue remaining after mild hydrolysis of pentosans from corn-cobs is described. The process avoids the use of autocalves by pressing the acidified lignocellulosic mass at a moderate temperature. The effects of different variables on the yields were studied. Under the best conditions tested, 65% of polymeric potential sugars in the residue were recovered as fermentable sugars in the extract. This is the last stage of a complete procedure set up to obtain maximum yields of carbohydrates from agricultural wastes (soluble sugars, pentoses for chemicals, and glucose from cellulose for fermentations).