The endocranial matrix surfaces of parietal bones of 2-week old Albino Wistar rats were partly denuded of osteoblasts and then cultured for various periods up to 24 h, in control or PTE-enriched medium. They were examined by scanning electron microscopy and evidence for cell locomotion was found. Osteoblasts traversed the denuded bone surface and cut edges of bone in either medium, and cells also migrated out from vascular channels. Glass spicules were placed on the otherwise undisturbed osteoblast layer in similar organ cultures for 2, 3 or 5 days. Osteoblasts migrated from the bone to populate the glass, negotiating any angle. The cells in PTE-enriched media were always aligned parallel to one another and elongated, tended to align with the edges of the glass and, in time, formed a substrate of aligned fibrils whose axes were parallel to those of the cells. Osteoblasts in control medium on glass showed variable degrees of alignment and elongation and were less influenced by edges of the glass. Non-locomotory, nearly equidiametrical cells on glass in 5d control cultures had formed a substrate of randomly oriented fibrils. Migrating osteoblasts on bone matrix did not have leading edge ruffles; isolated, migrating ones on glass did.