Pig follicular oocytes with cumulus cells were cultured in different maturation media, modified tissue culture medium 199 (TCM-199B) and BSA-free Whitten's medium (mWM), containing gonadotropins (10 IU eCG/ml + 10 IU hCG/ml) and/or 10% (v/v) fetal calf serum (FCS) or 10% (v/v) pig follicular fluid (PFF). After 48 h of culture, complete (degree +3) cumulus expansion was observed in oocytes cultured in both kinds of media supplemented with gonadotropins together with FCS or PFF. However, when oocytes were cultured in media with gonadotropins only, moderate (degree +2) cumulus expansion was observed in TCM-199B, while no (degree 0) cumulus expansion was observed in mWM. The proportions of metaphase II (M-II) oocytes were significantly (P<0.01) higher in both media in the presence of gonadotropins (61-95%) than in their absence (22-35%), irrespective of FCS or PFF supplementation. The addition of FCS or PFF to the media containing gonadotropins increased the proportion of oocytes reaching M-II in mWM but not in TCM-199B. When gonadotropin-containing media were used, the rate of male pronuclear formation in oocytes fertilized in vitro was significantly higher (P<0.05) in TCM-199B with PFF (70%) than with FCS (30%) although the value in PFF did not differ statistically from that (50%) in unsupplemented medium. In mWM, FCS did not support penetration of oocytes by spermatozoa, while PFF supported high rates of penetration (72%) but not male pronuclear formation. These results indicate that gonadotropins and/or FCS and/or PFF affect nuclear and cytoplasmic maturation of pig oocytes in different ways.