Poly(L-lactic acid)-titanium dioxide nanocomposites (with various loadings of TiO2: 0.5, 1, 2, 5, and 10 wt %) were produced by solution casting method. The influence of TiO2 on thermal properties and crystallinity of PLA was investigated by DSC and FTIR spectroscopy. The TiO2 nano filler has no significant influence on the characteristic temperatures (T-g, T-c, and T-m), but has high impact on the crystallinity of these systems. The degree of crystallinity X-c significantly increases for PLA nanocomposites loaded with up to 5 wt % of TiO2, while for 10 wt % load of TiO2 it drops below Xc of the pure resin. The degradation of the prepared composites was evaluated hydrolytically in 1N NaOH, enzymatically in a-amylase solutions, and under UV irradiation. The catalytic effect of TiO2 nano particles on the degradation processes under UV light exposure (lambda = 365 nm) and hydrolytic degradation was confirmed with the increase of the filler content. The opposite effect was identified in enzymatic degradation experiments. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 2187-2193, 2012