An experimental investigation was conducted to study crack growth transients produced when a sustained load hold time interrupts elevated temperature fatigue. Crack propagation testing of the superalloy INIOO was performed in air at 732°C for hold times ranging from 1 to 30 min, and the effects of load amplitude, specimen thickness, and frequency of fatigue cycling were examined. Using fractographic methods crack growth transients were observed for both sustained load crack growth following fatigue and fatigue crack growth following sustained loading. The beginning of the hold time was characterized by initially rapid crack growth that decayed to a steady-state behavior in approximately 5 min. Following the hold time, a retardation in crack growth rate was observed that partially counterbalanced the earlier, rapid crack growth. Compliance measurements used to monitor fatigue crack growth following a hold time underestimated the actual crack length as determined fractographically. In light of the observed crack growth transients associated with individual hold times, a discussion is presented of crack growth data generated under a loading sequence composed of short blocks of fatigue cycles separated by periodic hold times of short duration.