Dissociated neurons from embryonic chick dorsal root and sympathetic ganglia (peripheral neurons) and from spinal cord and retina (central nervous system neurons) were cultured on plastic substrata treated with purified fibronectin and laminin. Both central and peripheral neurons attached to and extended neurites on laminin. In contrast, only peripheral neurons initiated neurites on fibronectin; central neurons cultured under identical conditions aggregated into clusters and did not extend neurites. Neurite length, number of neurites initiated, and extent of neurite branching on fibronectin- and laminin-treated substrata were evaluated and compared with similar measurements of neuronal response to poly-L-lysine-treated plastic. Poly-L-lysine provides an adhesive surface for neurite elongation, but fibronectin and laminin appear to promote more rapid neurite elongation. Our observations suggest that neuronal interaction with these glycoproteins may involve neuron-specific cell surface components. These responses to laminin and fibronectin in vitro may be related to the presence or absence of these glycoproteins in specific extracellular environments during specific developmental stages.