Rolling-element fatigue studies were conducted with VIM-VAR AISI M-50, EFR 18-4-1, and VAR 18-4-1. Groups of 12.7-mm (1/2-in.) diameter balls of each material were tested in the five-ball fatigue tester. Test conditions included a load of 1540 N (347 lbf) giving a maximum Hertz stress of 5520 MPa (800 000 psi), a shaft speed of 10 700 rpm, and a contact angle of 30 deg. Tests were run at a race temperature of 339 K (150 deg F) with a type II ester (MIL-L-23699) lubricant. The rolling-element fatigue life of VIM-VAR AISI M-50 was not significantly different from that of EFR 18-4-1 or VAR 18-4-1 based on a statistical comparison of the test results.