Abstract: A polymer lactide is prepared by the polymerization of meso-3,6-dimethyl-1,4-dioxane-2,5-dione or mesodilactide and, if desired, other monomers. The mesolactide monomer has preferably a free acid content of less than 1 meq/kg dilactide and is then polymerized in a manner known per se. The compositions containing polymesolactide obtained according to this process do not posess the typical characteristics of poly-DL-lactide, poly-D-lactide or poly-L-lactide. A shorter degradation time of a substrate based on the present polymer is unofficial for several purposes. The present polymers have a good biocompatibility and are thus suited for bone plates, clamps and sutures and controlled release of biologically active compounds. The present polylactides and/or copolymers thereof have the benefit of a good biodegradability, biocompatibility, non-toxicity and non-mutagenicity.