Two 50th percentile anthropomorphic test devices are specified as alternate test devices for FMVSS 208 compliance testing. These test devices are commonly known as the Hybrid II and the Hybrid III dummies. The designs of the two dummies are different, representing the state-of-the-art in the time frame of their designs. The trajectory differences between the two dummies have been published in the literature, but response differences, e.g., HIC and chest acceleration are not available in the literature.To quantify response differences between the two dummies, a series of sled tests with open bucks and with bucks simulating vehicle interior were conducted with restrained dummies. Additional crash tests were also conducted with the two dummies.This paper reports on an analysis of the data from the above series of tests. The data indicate that in non-head contact simulations with belt restraint systems, Hybrid III HIC's are nearly 50% higher than Hybrid II HIC's. Additionally, in the above test condition, Hybrid III chest accelerations are nearly 27% higher than Hybrid II chest accelerations. With air bag restraint systems, statistically significant differences in dummy responses were not observed due to limited test conditions.