We have investigated the morphology and migratory behavior of quail neural crest cells on isolated embryonic basal laminae or substrata coated with fibronectin or tenascin. Each of these substrata have been implicated in directing neural crest cell migration in situ. We also observed the altered behavior of cells in response to the addition of tenascin to the culture medium independent of its effect as a migratory substratum. On tenascin-coated substrata, the rate of neural crest cell migration from neural tube explants was significantly greater than on uncoated tissue culture plastic, on fibronectin-coated plastic, or on basal lamina isolated from embryonic chick retinae. Neural crest cells on tenascin were rounded and lacked lamellipodia, in contrast to the flattened cells seen on basal lamina and fibronectin-coated plastic. In contrast, when tenascin was added to the culture medium of neural crest cells migrating on isolated basal lamina, a significant reduction in the rate of cell migration was observed. To study the nature of this effect, we used human melanoma cells, which have a number of characteristics in common with quail neural crest cells though they would be expected to have a distinct family of integrin receptors. A dose-dependent reduction in the rate of translocation was observed when tenascin was added to the culture medium of the human melanoma cell line plated on isolated basal laminae, indicating that the inhibitory effect of tenascin bound to the quail neural crest surface is probably not solely the result of competitive inhibition by tenascin for the integrin receptor. Our results show that tenascin can be used as a migratory substratum by avian neural crest cells and that tenascin as a substratum can stimulate neural crest cell migration, probably by permitting rapid detachment. Tenascin in the medium, on the other hand, inhibits both the migration rates and spreading of motile cells on basal lamina because it binds only the cell surface and not the underlying basal lamina. Cell surface-bound tenascin may decrease cell-substratum interactions and thus weaken the tractional forces generated by migrating cells. This is in contrast to the action of fibronectin, which when added to the medium stimulates cell migration by binding both to neural crest cells and the basal lamina, thus providing a bridge between the motile cells and the substratum.