The effects of epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) on the in vitro maturation of porcine oocytes were examined. Oocytes obtained from the ovaries of slaughtered prepubertal gilts were matured in modified Medium 199 supplemented with 25% porcine follicular fluid and gonadotropins, and fertilized in vitro. Oocytes were either fixed 16 h later to assess fertilization or cultured for 7 days to assess embryonic development. In Experiment 1, the addition of EGF to maturation medium increased the percentage of meiotically mature oocytes (88% v. 70%; P < 0.001) but did not affect the proportion of fertilized or cleaved oocytes. Blastocysts derived from oocytes matured in medium supplemented with 10 ng mL(-1) EGF had a greater number of cells compared with those of control blastocysts (51.1+/-5.1 v. 36.0+/-3.1; P < 0.02). In Experiment 2, the addition of IGF-I to maturation medium had no effect on meiotic maturation, fertilization or embryonic development. Our findings demonstrate that EGF plays an important role in both the meiotic and cytoplasmic maturation of porcine oocytes in vitro.