Polysilicon microfracture specimens were fabricated using surface micromachining techniques identical to those used to fabricate microelectromechanical systems (MEMS) devices. The nominal critical J-integral (the critical energy release rate) for crack initiation, J c , was determined in specimens whose characteristic dimensions were of the same order of magnitude as the grain size of the polysilicon. J c values ranged from 16 to 62 N͞m, approximately a factor of four larger than J c values reported for single crystal silicon.