Tenascin-C is present within the developing central nervous system during oligodendrocyte precursor cell migration. Tenascin-C is antiadhesive for oligodendrocytes, suggesting a role in controlling the migration of oligodendrocyte precursors and hence the pattern of myelination. Here we show directly that tenascin-C is a repulsive (or antiadhesive) substrate for primary oligodendrocyte precursors and also inhibits their migration. The antimigratory effect of tenascin-C on oligodendroglia is mediated through two distinct mechanisms; reduced substrate adhesion and a direct inhibition of cell migration that is independent of adhesion. These two effects map to different domains of the tenascin-C molecule. The repulsive effect maps to the EGF-like repeats and the alternatively spliced FN III repeats while the direct migration-inhibiting effect maps to FN III repeats 7-8. Our results show tenascin-C to have the novel property of inhibiting migration by both adhesion-dependent and adhesion-independent mechanisms, with different regions of the same molecule responsible for the two effects.