Charcot-Marie-Tooth disease (CMT) affects the peripheral nervous system. It is generally inherited in an autosomal dominant pattern, but also is inherited in recessive or an X-linked pattern. The degree of severity can vary greatly from patient to patient, even within the same family. Traditionally, the different classes of CMT have been divided into demyelinating forms and axonal forms. Until 10 years ago, the genetic basis of CMT disease was largely unknown. An intrachromosomal duplication on chromosome 17 was found in 1991, and a point mutation in the peripheral myelin protein-22 gene was discovered in 1992. The work starts a new stage of the molecular basis of this large group of peripheral neuropathies. In this review, we will summarize what is known today about the genetics of CMT, and what we have learned about the underlying disease mechanisms.