The present study was conducted to investigate the effects of cumulus cells and porcine follicular fluid (pFF) on plasminogen activator (PA) activity and oocytes maturation in vitro in the pig. The cumulus-oocyte complexes (COCs) and denuded oocytes (DOs) were incubated in NCSU-23 medium with or without 10% pFF for 0, 24, or 48 hr. In the presence of cumulus cells, the proportions of oocytes matured to metaphase-II stage were significantly (P<0.05) higher in medium with pFF than without pFF (69.8 vs. 37.7%, respectively). When COCs and DOs were cultured in the presence of pFF, tissue-type PA (tPA), urokinase-type PA (uPA), and tPA-PA inhibitor (tPA-PAI) were observed in COCs, and PA activities were higher at 48 hr than 24 hr. When COCs and DOs were cultured in the absence of pFF, tPA and tPA-PAI were observed in COCs, and PA activities were increased as duration of culture increased. No PA activities were detected in DOs regardless of pFF supplementation. When porcine oocytes were cultured in the presence of pFF for 24 and 48 hrs, the activities of tPA-PAI, tPA, and uPA were observed in both COCs and DOs. In medium of absence of pFF, PA activities were observed in oocytes with cumulus cells only. On the other hand, three plasminogen-dependent lytic bands (tPA-PAI, tPA, and uPA) were observed in pFF cultures. Particularly uPA activity was higher than the other kinds of PA activity. When oocytes and cumulus cells were separated from porcine COCs at 0 hr of culture, tPA-PAI, tPA, and uPA were detected in cumulus cells at 48 hr of culture, but no PA activities were in DOs. The presence of pFF and cumulus cells in maturation medium stimulated not only nuclear and cytoplasmic maturation in porcine COCs, but also PA production by cumulus cells and COCs. It is possible that PAs produced by cumulus cells migrated through the gap junction between oocyte and cumulus cells. These results suggest that porcine oocytes have no ability to produce PA themselves.