This study was carried out to examine whether EGF, IGF-I and insulin could directly modify the meiotic maturation of bovine denuded oocytes in vitro, and to see whether the stimulatory effect of EGF on bovine oocyte meiotic maturation is mediated through the tyrosine kinase pathway. In the first three experiments, cumulus-oocyte complexes (COCs) were removed from their cumulus cells and the denuded oocytes were cultured in vitro with various concentrations of EGF, IGF-I and insulin. Nuclear maturation was examined after 24 h of culture. EGF, IGF-I as well as insulin effectively increased the proportion of oocytes developed to the metaphase II stage. The higher rates of MII oocytes were achieved with 50 ng/ml EGF (69.4%), 100 ng/ml IGF-I (66.1%) or 5 μg/ml insulin (63.1%) compared to about 48 to 54% in the controls. In experiment 4, whereas EGF significantly (p<0.05) increased the proportion of MII oocytes for denuded oocytes derived from the collected COCs, it had no stimulatory effect on MII formation of oocytes found cumulus-free or denuded at the time of aspiration. In experiment 5, with erbstatin, a specific tyrosine kinase inhibitor, the stimulatory effect of EGF on meiotic maturation of denuded oocytes was abolished. These results indicate that EGF, IGF-I and insulin could directly stimulate meiotic maturation of bovine denuded oocytes removed from the surrounding cumulus cells after oocyte collection. Moreover, the results also suggest that the stimulatory effect of EGF on bovine denuded oocyte meiotic maturation is mediated by the tyrosine kinase signal transduction pathway.