Process for the preparation of lactide

A continuous or semicontinuous process for preparing L(-) or D(+)-lactide of substantial optical purity, wherein L(-) -polylactic acid is employed as the starting material to make L(-) lactide and D(+)-polylactic acid is employed as the starting material to make D(+)-lactide, wherein the starting materials are of 90% optical purity, and wherein the polylactic acid is heated to about 130 .degree. to 230.degree. C., under reduced pressure, in the presence of about 0.05 to 1.0 per cent by weight of a catalyst selected from the group consisting of tin dust, tin halide and organic tin compounds derived from C.sub.1 -C.sub.20 carboxylic acids.