The polymerization reaction of d,1-lactic acid through polycondensation by direct melting is very important when low molecular weight polymers are desired, mainly for biomedical uses due to the easiness and low cost of process. And example of this is the manufacture of controlled delivery devices for drugs. In this work the steps involved on the polycondensation (oligomerization and polymerization) to obtain PLA were studied. The oligomerization was studied in a narrow range of temperatures 100-150°C where the kinetics model that describes the reaction is a kinetic law of powers of third order, with Ea and 125 REVISTA COLOMBIANA DE QUIMICA, VOLUMEN 35, No. 2 DE 2006 o rg an ic a y b io q u im ic a 1 Departamento de Ingenieria Quimica, Universidad Nacional de Colombia, sede Bogota, Bogota, Colombia jepinzonri@unal.edu.co 2 Departamento de Investigacion y Desarrollo Chalver Laboratorios, Bogota Colombia. preexponential factor at 298.15K being 22,7 kcal/molK and 3.28x10 L/molh respectively. For the polymerization step was studied the influence of temperature, the catalyst ratio (SnCL2.2H2O) and the time of reaction at the glassy transition temperature.