An experimental and theoretical modeling study is presented on the kinetics of reversible oligomerization of L-lactic acid and the formation of L-lactide in closed reactors with SnCl2 center dot 2H(2)O/p-toluenesulfonic acid as a binary catalyst mixture. The experimental data and model simulations indicate that about 10 wt % L-lactide is produced by the cyclization of two repeating units of poly(L-lactic acid) at the chain end during the oligomerization process. The effects of the catalyst and reaction temperature at 160-200 degrees C on the discoloration of the reaction mixture have also been investigated, and it was observed that the discoloration of the reaction mixture was quite significant in the presence of the catalyst at high temperatures. The relevant kinetic parameters for the chain-growth reaction as well as cyclic L-lactide formation reaction have been estimated for both noncatalyzed and catalyzed reversible oligomerization reactions.