Cyclic deformation behavior and fracture mechanisms of Ferrovac E iron under low cycle fatigue conditions are studied at temperatures ranging from 23 to 540 C, cyclic deformation rates from 4 × 10^-4 to 2 × 10^-1 s^-1, and strain ranges from 0.010 to 0.040. The stress response during strain cycling shows three stages, primary hardening, steady state behavior, and secondary hardening. Both the onset and duration of secondary hardening are dependent on deformation rate and temperature through the process of dynamic strain aging. Stress response sensitivity to deformation rate increases under conditions which permit changes in both internal and effective stress components. There is a variation in the internal stress component at the blue brittleness temperature (370 C) caused by an increase in total dislocation density due to dynamic strain aging. However, at higher temperatures (485 to 540 C) a variation in the internal stress component is caused by accelerated thermal recovery. Steady state cyclic deformation in this temperature range is observed to be consistent with models for steady state creep and hot-working. The fracture mechanism and fatigue life are mainly influenced by the characteristics of stress and strain redistribution and the inhomogeneity of plastic-strains. This inhomogeneity of deformation results from dynamic strain aging effects during fatigue. A parameter which controls stress response, fatigue behavior, and fracture mode under dynamic strain aging conditions is presented.