Abstract Specimens of SAE 1045 steels with and without 0.10 wt pct of vanadium were surface-induction hardened with the same set of processing parameters. Fully martensitic microstructures formed from austenitic microstructures with a common grain size of 10 μm. Specimens were induction tempered at 270 °C for 5 s or at 220 °C for 4 min; a third set of specimens was furnace tempered at 215 °C for 10 h. Near-surface hardness of tempered specimens was between 586 and 620 Vickers hardness (about 55 Rockwell-C hardness), with statistically higher values for the 10V45 steel. Axial residual stresses in the range of -690 to -796 MPa were measured at specimen surfaces, and similar average values were reported for both steels. Analyses revealed that the 5-s/270-oC condition was the most highly tempered, and the least tempered was the 4-min/220-oC condition. Load-controlled, fully reversed, cantilever bending-fatigue tests were conducted with notched specimens. Fatigue failures were initiated at multiple sites at notched surfaces in association with near-surface oxide inclusions. Endurance limits ranged from 470 to 605 MPa, with similar average values for both steels. Ratios of adjusted endurance limit to calculated ultimate tensile strength were approximately 0.35. A trend of increased endurance limit with a decrease in the degree of tempering was established for 1045 steel, but not for 10V45 steel. The least-tempered 4-min/220-oC condition of 1045 steel exhibited an unexpectedly high endurance limit of 605 MPa, a result ascribed largely to the higher surface residual stress for this condition. Similarly superior performance in the 10V45 steel for this tempering condition was not observed. The latter outcome was attributed to embrittlement at prior austenite grain boundaries owing to a higher level of phosphorous.