In the present work, the dynamic compression behaviour of austenitic steel AISI 321 is obtained at elevated temperatures up to 750 oC using the Split Hopkinson Pressure Bar. The material showed strain rates sensitivity in the range from quasi-static up 6200 s-1. The role of strain-induced martensite transformation on strain-hardening was studied. The % of the strain-induced martensite was found to depend on the test temperature and amount of strain. In the dynamic regime,~ 2800-5000 s-1, the amount of %transformed strain-induced martensite depended only on the test temperature and not the strain rate. This indicated that the strain-induced martensite transformation did not contribute to the drop in the rate of strain hardening at intermediate strain rates of ~2800 s-1 at elevated temperatures and its increase at higher strain rates of 5000 s-1. The Johnson-Cook material model was fitted to the obtained results and model constants were obtained using two different fitting approaches.