During skin repair both keratinocytes and fibroblasts migrate into the wounded area. In the process of cell migration, controlled proteolytic degradation of the extracellular matrix occurs. It has been suggested that the plasminogen activator system is involved in such proteolytic processes occurring during wound healing. The role of plasmin, urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator (t-PA) in keratinocyte and fibroblast migration in vitro was examined in the present study. Confluent cultures of normal human keratinocytes, human squamous cell carcinoma (SCC-4), SV40 transformed keratinocytes (SVK-14) and human fibroblasts were mechanically wounded and the repopulation of the denuded area was examined. Migration of cells into the denuded area could be inhibited by neutralizing antibodies against t-PA or u-PA, or the serine protease inhibitor Trasylol in all cell types studied. For detailed study on involvement of u-PA and t-PA in migration processes wounded cultures of SVK14 cells were used. Both t-PA and u-PA activity could be detected at the migrating edge of SVK14 cultures as revealed by zymography and by immunocytochemistry using polyclonal antibodies. Our results demonstrate the direct involvement of not only u-PA but also t-PA in migration of keratinocytes and fibroblasts in wounded cultures in vitro.