A nickel-base superalloy, Nimonic 90, was subjected to room-temperature low-cycle fatigue under constant total strain control. Cyclic stress response was investigated as a function of the total strain range. Hardening was attributed to slip band formation and softening to the shearing of γ′ precipitates Slip band spacing decreased with increasing strain range. Two-slope behaviour or bilinearity seen in Coffin-Manson and cyclic stress-strain plots has been attributed to a change in the deformation mode with increasing strain range.