In line with the need for a suitable dynamic test procedure to determine the reaction of seat belt hardware and overall effectiveness of the seat belt or harness in constraining the vehicle occupant at various crash angles, a dynamic seat belt tester has been developed by the National Bureau of Standards. This tester was designed to provide a motion as stipulated by the proposed SAE dynamic specifications, and to reduce the cost, size, and power required in previously designed testers based on the sled principle. A progress report on the performance of this test device to date is given, including a description of its major components and general operation.