In load-controlled tensile tests at 4K, an abrupt and large discontinuous yielding behavior occurs, which remarkably differs from the discontinuous yielding observed in displacement-controlled tests. The tensile properties under a load control mode may, therefore, be different from that obtained under a displacement control mode. A series of tensile tests has been performed in this regard using 304 and 316 metastable austenitic stainless steels at 4K under a load control mode to examine the effect of specimen size and loading rate on the discontinuous yielding behavior. Four different stress rates ranging from 0.154 to 154 MPa/s were used, while the diameters of tensile specimens were 4.5, 6.35 and 8㎜. Both the stress rate and the specimen diameter were found not to affect the yield strength. However, the stress and strain at the onset of discontinuous yielding decreased as the stress rate and specimen diameter increased. The discontinuous yielding behavior under a load control mode was then compared with that under a displacement control mode.