In response to injury, vascular smooth muscle cells (VSMC) are thought to migrate toward the area of damage, where they participate in the reparative process. We have recently identified and isolated two distinct cell types (VSMC and type 2 cells) from the tunica media of canine carotid artery and saphenous vein. The purpose of these experiments was to determine whether both cell types were able to migrate in response to a variety of chemoattractants. A multiwell Boyden chamber and a wound migration assay were used to assess the migratory ability of these cells in vitro. The results indicated that VSMC did not exhibit directed migration in response to either 10% fetal bovine serum or platelet-derived growth factor (PDGF)-AB. In contrast, type 2 cells migrated to serum, PDGF-AB, and PDGF-BB but not to PDGF-AA, endothelin (ET)-1, or ET-3. No difference in migratory ability was detected between type 2 cells isolated from carotid arteries or saphenous veins. It is concluded that the migratory ability of cells within the tunica media of vessels from adult animals are not equal, suggesting that only selected cells may participate in vascular wall repair.