Steels which contain 0.085 C, 0.36 C, and 0.38 C were intercritically annealed at 745, 760, 775, and 790 degrees C for 30 min followed by water quenching to obtain dual-phase (martensite-plus-ferrite) structure. It was found that the volume fraction of martensite increased with increasing annealing temperature. Rotating bending tests (10 million cycles) were conducted on the as-received materials and the dual-phase steels specimens selecting completely reversed cycle of stress. It was seen that the fatigue strength of dual-phase steels increased when compared with as-received materials. The highest fatigue strength was observed in the intercritically annealed steels at 760 degrees C. The fatigue strength of these steels increased at the annealing temperature up to 760 degrees C and decreased at the annealing temperatures higher than 760 degrees C. (C) 2006 Elsevier Ltd. All rights reserved.