The effect of hydrothermal exposure on the ability of the interface to transfer shear stresses in graphite/epoxy composites under compression is reported. Hydrothermal exposure caused a drop in the ability of the interface to transfer shear stresses from 130 to 15 MPa and increase in the average fragment length from 80 to 1000 mu m The impact of hydrothermal exposure on the composite interfacial behavior is compared with that for composites loaded in tension. The results showed that the interfacial degradation is more severe for composites loaded in compression.