Abstract: Procedure to improve the area yield in the manufacture of leather consisting of a thermal treatment applied to the extended or stretched leather, before the operation of drying. During this treatment there should be no loss in the water content of the leather. The applicattion of this procedure in the manufacture of leather allows improvements to be obtained in the area yield of about ten percent and, when applied to dyed leathers, an improvement is obtained in the fixation of the products used in the wet phases and, therefore, an improvement in the fastness properties to rubbing at dry as well as wet conditions. The application of this procedure reduces the modulus of the leather for which its use can be especially interesting for leather destined for clothing, upholstery, and some types of footwear which require lower elasticity values.