Polylactide (PLA)/montmorillonite (MMT) cationic clay and PLA/hydrotalcite (HT) anionic clay composites at 5 wt% clay were melt compounded and characterized for morphology before and after hydrolytic degradation. Semicrystalline and amorphous polymers were used as well as noncalcined and calcined clays. The addition of cationic clays led to the formation of microcomposites, whereas the addition of anionic clays produced a much finer dispersion and enhanced polymer intercalation corresponding to that found in nanocomposites. Hydrolytic degradation rate constants of cationic microcomposites and, particularly, of anionic nanocomposites are lower than those of the unfilled polymers, possibly due to the reduction of the carboxylic group catalytic effect through neutralization with the hydrophilic alkaline filler. Comparison of calcined MMT and HT clays vs. their noncalcined counterparts suggest that calcination can further reduce hydrolytic degradation rates, particularly for semicrystalline PLA. Based on the calculated activation energies, the degradation kinetics did not differ significantly above and below the assumed T-g of 58-60 degrees C. The results of this work would be applicable to controlled release pharmaceutical formulations containing clay/drug combinations produced by melt compounding with a biodegradable polymer matrix. POLYM. ENG. SCI., 50:320-330, 2010. (C) 2009 Society of Plastics Engineers