This investigation examined carbon/epoxy and aramide/epoxy composites in interlaminar shear and in open-hole tensile tests at 90 to the unidirectional fibre orientation. Epoxy resin was also tested under tension. Photomicroscopy and the S.E.M. were used to study the fracture surfaces. Wet tests were performed to investigate the influence of moisture absorption on the strength of the composites. In the interlaminar shear tests shear crippling and interlaminar delamination were seen for most of the specimens. The value of the interlaminar shear strength did not change with the water absorption. In the open-hole tensile tests the moisture uptake increased the local plasticity of the resin and the size and number of voids in the material. In both the composites the interfacial bounding seemed to decrease owing to water absorption. Kink bands were found on the compression sides of the aramid fibres in both the wet and dry specimens.