The safety of passengers is very important during an automobile collision. Because the collision event involves high speed deformation, property data and deformation mechanisms of materials under high strain rate conditions are needed to choose proper materials for automobiles. Therefore, in this study, dynamic mechanical properties of low carbon TRIP steels with varying retained austenite stabilities were evaluated over a wide range of strain rates using a high-velocity hydraulic tensile testing machine. Tensile tests were performed at strain rates ranging from 10-2 to 6x102/sec using normal ASTM E-8 specimens with an elastic strain gage attached to the sample grip end to measure load and a plastic strain gage mounted on the gage section to measure strain precisely. Ultimate tensile strengths, strain rate sensitivities, and strain hardening behaviors are reported. The strength of TRIP steels increased with increasing strain rate, that is, positive strain rate sensitivity was observed.