Single-edge-notched specimens of a structural carbon steel and a low-alloy steel were fatigued under axial loading. The initiation and propagation behavior of short fatigue cracks emanating from a sharp notch was investigated. The resistance-curve (R-curve) method was used to predict the fatigue thresholds of notched members. The R curve was constructed in terms of the experimentally determined threshold value of the maximum stress intensity factor which was the sum of the threshold effective stress intensity range ΔKeffth and the opening stress intensity factor Kopth. The value of ΔKeffth was constant and the R curve was independent of crack length and notch geometry. The predicted values of the fatigue limit for crack initiation, the fatigue limit for fracture, and the nonpropagating crack length agreed well with the experimental results. The effect of the material property or Vickers hardness on the fatigue notch sensitivity was discussed on the basis of the R-curve method. A simplified method to determine the R curve using Vickers hardness or the tensile strength was proposed for design applications.