The findings from an experimental study to investigate cumulative seismic damage in reinforced concrete columns are presented. Fourteen identical half-scale concrete columns were fabricated and tested to failure. Results from Phase I testing, which included constant amplitude tests to determine the low-cycle fatigue characteristics of the rectangular concrete column, were presented in a companion paper. This paper summarizes results of variable amplitude tests. The imposed displacement histories were obtained from analytical simulations of the model column subjected to a series of earthquakes. Test observations indicate that failure is generally initiated by confinement inadequacy and the rupture of the transverse hoop reinforcement. The tests also demonstrated the potential for low-cycle fatigue fracture of the main longitudinal steel when the specimen was subjected to relatively larger displacement amplitudes. A fatigue-based damage model, derived from the constant-amplitude tests completed in Phase I testing, was applied to the observed response of the three specimens tested in this phase. Findings from the study indicate that the energy capacity of members is ductility-dependent and that fatigue-based damage models offer a reliable means of assessing seismic structural performance.