The structure of the cuticle from the "Pompeii worm" Alvinella pompejana and Riftia pachyptila is presented. The cuticle structure of Alvinella is similar to that of other annelid species, whereas that of Riftia presents patterns which are observed in biological analogues of cholesteric liquid crystals. The amino acid composition of a vestimentiferan cuticle is presented for the first time and compared with that of other invertebrates.