Rat Schwann cells are neural crest derivatives that ensheathe and myelinate axons of peripheral nerves. Each Schwann cell wraps around the shaft of an individual peripheral axon, forming myelin sheaths along segments of the axon. Schwann cells play important roles in the development, function, and regeneration of peripheral nerves. When an axon is dying, the Schwann cells surrounding it aid in its digestion, leaving an empty channel formed by successive Schwann cells, through which a new axon may then grow from a severed end. There is a tight regulation in the number of Schwann cells in the peripheral nerves. Growth factors such as PDGF, FGF, neuregulin, and others stimulate Schwann Cell proliferation in vitro. Schwann cells provide a relatively simple, well-defined, and accessible mammalian model for the study of a number of developmental questions. It is also of particular clinical importance to understand the biology of Schwann cells, not only in the context of neuropathies and nerve regeneration, but also because the cells or their precursors may play an important role for implants to facilitate repair in the CNS.