An experimental study was carried out for the corn cobs thermal conversion to obtain the maximum content in lactic acid. For this purpose, under the same conditions (275 degrees C and 30 min) different concentrations of Ca(OH)(2) as alkaline catalyst were used (from 0.32 M to 1 M). The maximum content of lactic acid (6.72 +/- 0.31 g/L) was obtained with 0.7 M of Ca(OH)(2). With this catalyst concentration, different reaction conditions were used (250, 275 and 300 degrees C and 15,30 and 45 min). The optimal conditions to produce the highest yield of lactic acid from corn cobs in alkaline conditions were determined at 300 degrees C and 30 min, achieving 44.76 +/- 2.59% respect to the total cellulose and hemicellulose contained in the initial corn cobs (7.38 +/- 0.43 g/L of lactic acid). (C) 2011 Elsevier B.V. All rights reserved.