The fatigue tests on 0.23%C steel were carried out with two superimposed cyclic Ioadings with different repeating speeds, in the case when the repeating speed of the secondary stress, the fast stress wave σ_a2, was 2000c/min, and the primary speed, the slow one σ_a1, was 50 or 420c/min. The ratios of those stress amplitudes σ_a2/(σ_a1+σ_a2) were selected in the range from 0.75 to 0.27. Those complex stress patterns were analyzed by the peak pair count method, and the fatigue lives and endurance limits were calulated with the formula ; the method and the formula were proposed by the authors. The calculated values agreed well with the experimental results, even in the case where the primary stress amplitude was larger than the secondary one. It was also clarified that the peak pair count method is more widely applicable to those stress patterns than other count methods.