In this laboratory activity for introductory organic chemistry, students carry out the tin(II) bis(2-ethylhexanoate)/benzyl alcohol mediated ring-opening polymerization of lactide to form the biodegradable polymer polylactide (PLA). As the mechanism of the polymerization is analogous to that of a transesterification reaction, the experiment can be used to demonstrate reactions of carboxylic acid derivatives. The polymerization can be successfully carried out using standard teaching laboratory (non-Schlenk) conditions. Analysis of polymer stereochemistry by [to the first power]H NMR and a discussion of the effect of monomer stereochemistry on the stereochemistry of the polymer are included in the experiment. The effect of adventitious water on the rate of the polymerization and the number-average molecular weight, M[subscript n] of the resulting polymer are discussed in the Supplemental Material. (Contains 1 figure and 1 note.)