Damage mechanisms and accumulation, and associated stiffness and residual strength reductions, were studied in cross-ply graphite/epoxy laminates under cyclic tensile loading. Stress-life data were fitted by straight lines on a log-log scale. The fatigue sensitivity decreases with the number of contiguous 90-deg plies. Five different damage mechanisms were observed: transverse matrix cracking, dispersed longitudinal cracking, localized longitudinal cracking, delaminations along transverse cracks, and local delaminations at the intersections of longitudinal and transverse cracks. A cumulative damage model is proposed based on residual strength and the concept of equal damage curves.