The fracture and yield strength of polyetherimide was evaluated over a temperature range of 23 to 140degreesC for materials with number-average (M-n) and weight-average molecular weight (M-w) ranging from 15.6 to 22.8 and 36.6 to 52.3 kg/mol, respectively. The brittle-to-ductile transition temperature, where an equal probability exists that an impact will result in a brittle or ductile failure, was determined by evaluating the temperature at which fracture and yield strength are equal. The transition temperature decreased from 155 to 60degreesC with increasing molecular weight and provided a measure of relative ductility between material samples. As a case study, the practical impact strength of an injection-molded food service tray was determined at 20degreesC and correlated with fracture strength as a function of molecular weight. (C) 2004 Wiley Periodicals, Inc.