The durability of polylactide (PLA) blended with polycarbonate (PC) was assessed by exposure to conditions of elevated temperature and humidity over a period of several weeks. Mechanical performance, moisture absorption, chemical composition, and thermal properties were monitored as a function of continuous conditioning at 70 degrees C and 90% relative humidity (RH). All PLA and PC/PLA blends showed significant moisture absorption and hydrolysis, resulting in degradation of properties. Furthermore, while the addition of PC was intended to improve the durability of the blend over neat PLA, it was found that the hydrolysis products of PLA accelerated the degradation of PC itself. This study shows for the first time the hydrolysis behavior of PC/PLA blends in an increasingly acid environment during heat and humidity conditioning. These injection-molding grades of PLA-based resins are currently not suitable for use in applications that require long-term durability in environments subject to elevated temperature and humidity, such as automotive interiors. Further material formulation work is required before use in injection-molded applications for automotive. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013