We have been studying how and when the different peripheral glial cell lineages individualize during avian embryonic development. Three different and complementary experimental approaches were used for this purpose: 1) the quail/chick chimera system allowed the tracing in vivo of the origin of the various types of peripheral glial cells (Schwann cells of nerves, satellite glial cells of sensory and autonomic ganglia, and enteric glial cells), and the analysis of the non-neuronal cell population of ganglia; 2) characterisation of early cell-type specific markers that discriminate between the different glial cell subpopulations; and 3) analysis of the progeny of neural crest cells in clonal cultures. As a result of these approaches, two novel glial-specific markers, expressed earlier than any previously described myelin components, have been identified and partly characterised. The divergence of glial and neuronal cell lineages is a process that is not completely terminated during the phase of neural crest migration. Whereas some cells are apparently already totally committed to a glial fate at this stage, others retain dual neuronal/glial potentialities.