Premalignant oral lesions have a high incidence of recurrence and progression to malignant disease and, although studies have shown the contribution of transforming growth factor β (TGF-β) to cancer progression, none have been conducted with premalignant oral lesion cells to determine the impact of TGF-β in stimulating properties that are characteristic of more invasive cells. The present study focused on TGF-β-modulation of paxillin and the serine/threonine protein phosphatase PP-1, and the impact on cellular motility. These studies show that TGF-β stimulates premalignant lesion cell motility and up regulates expression of paxillin, as well as its co-localization with PP-1, while concurrently diminishing the level of paxillin serine phosphorylation. The TGF-β-mediated up regulation of paxillin and co-localization with actin, as well as the TGF-β-stimulated motility of premalignant lesion cells, were all blocked by inhibiting PP-1, indicating their dependence on PP-1 activity. These studies suggest interplay between TGF-β and PP-1 in promoting a more malignant phenotype in premalignant oral lesion cells.