In an attempt to improve fatigue and fracture resistance, a multiphase (ferrite-bainite-martensite) microstructure was developed in a V-bearing medium carbon microalloyed steel using a two-step cooling and annealing (TSCA) treatment following finish forging. The monotonic, cyclic stress-strain and low cycle fatigue behavior of this steel are reported. These results are compared with those of ferrite-pearlite and tempered martensite microstructures obtained by air cooling (AC) and quenching and tempering (Q&T), respectively. The tensile properties of the multiphase microstructure are superior to those of the ferrite-pearlite and the Q&T microstructures. Under cyclic loading, the ferrite-pearlite microstructure showed hardening at higher total strain amplitudes (≥ 0.7%) and softening at lower total strain amplitudes (<0.7%). The quenched and tempered and the ferrite-bainite-martensite (TSCA) microstructures displayed cyclic softening at all total strain amplitudes employed. Despite the cyclic softening, the ferrite-bainite-martensite structure was cyclically stronger than the ferrite-pearlite and the Q&T microstructures. Bilinearity in the Coffin-Manson plots was observed in Q&T and the multiphase TSCA conditions. An analysis of fracture surface provided evidence for predominantly ductile crack growth (microvoid coalescence and growth) in the ferrite-pearlite microstructure and mixed mode (ductile and brittle) crack growth in Q&T and the multiphase TSCA microstructures. © 2002 Elsevier Science B.V. All rights reserved.