Abstract: The end notched flexure (ENF) test was employed in an investigation of interlaminar fracture behavior in Mode II static and, fatigue loading for carbon/epoxy composites T300/M10 and HTA/6376. Under static loading,both of the materials exhibited bittle unstable and brittle stable behavior of crack growth. Stable Mode II crack growth was observed during fatigue loading with R=0.1 in a larger range of cyclic strain energy release rate. A consistent relation of crack growth rate to the cyclic strain energy release rate was obtained for the composites. Within the range of moderate crack growth rate,the data of Mode II fatigue crack growth obeyed a power law. The trend of reduction in crack growth rate data with degredation in cyclic strain energy release rate suggests the presence of a threshold strain energy release rate. Compared with T300/914C,HTA/6376 and T300/M10 have higher crack growth resistance.