Abstract Cockroach cuticles at various stages of development have been studied by chromatographic means and changes in the amino acid constituents have been found. These changes show a broad similarity to the changes seen in the cuticle of the developing puparium of Calliphora vomitoria ( Dennell, 1958). As in Calliphora, the cuticle of Periplaneta is capable of hydroxylating aromatic amino acids. Dihydroxyphenols are thus produced and are responsible for tanning the cuticle. An attempt, using the alkaline stannite reagent, to liberate the tanning quinone from its combination with the cuticular substrate, and to reduce it to its parent diphenol, resulted in the production of an amino phenol related to hydroquinone. This amino phenol appears to be identical with that produced when puparia of Calliphora and gelatin tanned with benzoquinone are similarly treated. The naturally occurring tanning phenol, therefore, appears to be hydroquinone. Comparison of the development of cuticle in the cockroach with that of Calliphora indicates that the tanning process in these two insects is fundamentally the same.