The nematode cuticle, like the endo- and exo-skeletons of other animals, is much more than just an inert structure against which muscles can act during locomotion. The cuticle performs complex roles in organismal physiology, protection from the environment, nutrition and excretion. Cuticle composition and structure reflects this complexity. In this chapter we review briefly the ultrastructure of the cuticle and examine the biochemistry and genetics of the components of nematode cuticles. We also discuss the cuticle as a dynamic structure, both over the lifetime of the nematode (through the moults) and on shorter timescales.