Polylactide (PLA) biopolymers are currently enjoying strong commercial interest as sustainable alternatives to commodity petroleum-based plastics in a wide variety of thermoformed packaging applications. Typically, the properties of unmodified PLA resins are sufficient to meet the performance requirements of these applications, providing the temperature-performance requirement remains less than about 50°C. For higher-temperature applications, the heat resistance of neat PLA resin is largely constrained by two fundamental physical limitations: a moderately low temperature glass transition (in the vicinity of 60°C) and a fairly slow crystallization rate. This presentation discusses the results of a development effort within NatureWorks LLC to improve the practical temperature resistance of IngeoTM PLA sheet in thermoformed packaging applications through modification of polymer composition, crystal nucleation, and the thermoforming process.