Tension-tension and compression-compression fatigue tests are conducted on cross-ply, angle-ply and quasi-isotropic carbon/epoxy (CFRP) laminates to characterize the damages which affect the fatigue strength. Two types of matrix-dominated damages, the transverse crackings and delaminations, are found to have significant effects on the final strength for the quasiisotropic laminates, while for the cross-ply and the angle-ply laminates, the correlations between these damages and the fatigue strength are not clear. Concise analyses of delamination onset and growth using the energy-release-rate approach are also given for quasi-isotropic laminates. Effects of stacking sequence, loading direction and ply thickness on delamination are clarified. The effective size of inherent free-edge flaws for delamination onset is also examined.