Comparative evaluation of a variety of anthropomorphic dummies undertaken by the Office of Vehicle Systems Research at the National Bureau of Standards indicates a wide range of dummy performance. Dynamic tests, which were conducted on the NBS Dynamic Seat Belt Tester, simulated an impact environment with the dummies restrained by lap belt alone, or combined lap and torso diagonal belts of the type used in American automobiles. A variety of dummies, varying in construction from the most rudimentary to the most sophisticated, was tested. Test parameters included variations in impact velocity and acceleration. Each dummy was tested with both types of restraints, and sufficient tests were made to demonstrate the ability of the dummy to reproduce its reaction performance.These tests indicate that even when dummies are subjected to carefully controlled impacts with skilled technical personnel following identical procedures, it is difficult to reproduce test results. Techniques which were used to control dummy performance and modifications which were incorporated to improve reliability of the dummies are discussed.