Abstract: Cyclic stress-strain behavior in pearlitic and tempered sorbitic eutectoid rail steels has been studied by Incremental Step Test technigue. It is shown that tempered sorbite exhibits only cyclic softening and simultirieous cyclic softening and hardening are observed in pearlite throughout the entire range of strain amplitudes investigated. Cyclic stress-strain properties in coase structure and pearlite are better than those in fine structure and tempered sorbite respectively. Critical strain amplitude of pearlite has been defined. The effects of properties on critical strain amplitude, and the relationship between microstructures, incremental step strains and cyclic stress-strain parameters have been investigated.