The use of a heterogeneous catalyst in the transesterification reaction of sunflower oil and waste oil for the production of methyl esters (biodiesel) has been studied. The basic hydrotalcite catalyst used showed a high activity for transesterification reactions in the operation conditions studied. The experiments were performed in a temperature range between 80 and 160 degrees C, in a batch reactor. The methanol/oil molar ratio in the reaction mixture and catalyst concentration ranges used were from 12:1 to 48:1 (mol/mol) and 3-12 (wt % of the initial vegetable oil mass) respectively. Calcined forms of the catalyst were tested. The catalyst was characterized with SEM, XRD, IR, and DTA-TG methods.