Abstract: Method of polymerization for producing polylactic acid of configuration L or D, with number-average molecular weight between 60 000 and 200 000 having an insertion defect rate between 0 and 0.5 wt. % of polylactic acid and a racemization defect rate between 0 and 2.5 wt. % of polylactic acid, characterized in that the method is a bulk process comprising contacting, at a temperature between 170 and 200° C. and for a reaction time between 5 and 75 minutes, the corresponding lactide of stereochemical configuration L-L or D-D having an optical purity of L or D of at least 99.5 wt. % with at least one catalyst in the presence of an initiator to form poly-L-lactic acid or poly-D-lactic acid.