The epicuticle of the cockroach consists of four well-defined layers, the cuticulin, paraffin, wax and cement layers. The cuticulin layer corresponds to the 'inner epicuticle' of blowfly larvae, and the paraffin layer to the 'outer epicuticle'. The information gained here on the cuticulin, wax and cement layers is in full agreement with that given by Wigglesworth (1933, 1947, 1948a) on these layers. Wigglesworth, however, did not recognize the existence of the paraffin layer. This layer corresponds in position to Wigglesworth's 'polyphenol' layer, which is not recognized here as a discrete and permanent structural layer of the epicuticle. Argentaffin material, regarded as polyphenol-containing by Wigglesworth, is suggested to occur only as a transient layer during the development of the cuticle. It is believed to penetrate and impregnate underlying layers of the cuticle and to consist of a protein with reducing properties, not due to the presence of a bound polyphenol, but in its own right.