Hopkinson split-bar tests were performed on Type 21-6-9 austenitic stainless steel from ambient temperature to 1023 K. These high-strain-rate tests (10/sup 2/ to 10/sup 4/ s/sup -1/) were compared with lower-strain-rate tests (10/sup -4/ s/sup -1/). The results indicate that over this temperature range, the strain-rate sensitivity of 21-6-9 is not strongly dependent on the strain rate. This suggests that the mechanism(s) of plastic flow at the higher rates is similar to that at the lower rates. This contention was corroborated by transmission electron microscopy