Abstract Undefined follicular factors that may influence nuclear maturation and/or cytoplasmic maturation are required during in vitro maturation of pig oocytes. Epidermal growth factor (EGF), insulin‐like growth factor‐I (IGF‐I), and dialysed porcine follicular fluid (dpFF) were evaluated for their effects on porcine oocyte nuclear maturation in vitro. In Experiment I, eight different maturation media were made in a split‐plot factorial design with dpFF (0% vs. 10% v/v dialyzed pFF) as the whole plot component, and EGF (0.0 vs. 50 ng/ml) and/or IGF‐I (0.0 vs. 100 ng/ml) as the factorial subplot component. Experiment II was a complete factorial design with dpFF and EGF. Pig follicular granulosa‐cumulus‐oocyte complexes (GCOC) were obtained from slaughterhouse ovaries, washed, and cultured at 38.5°C in a humidified incubator with 5% CO 2 in air for 42 h. Following culture, GCOC were mechanically stripped of granulosa‐cumulus cells and evaluated for nuclear maturation by light microscopy. In Experiment I, the percentage of Metaphase II oocytes for control, IGF‐I, EGF, and IGF‐I + EGF treatments without pFF were 50.7%, 52.6%, 80.9%, and 84.3% (control and IGF‐I groups significantly less, P <.001). The same treatments in the presence of pFF were similar and high (84.2, 84.9, 82.1, and 86.8%, respectively). Experiment II gave similar results. These results demonstrate that EGF, in the absence of pFF, promotes a similar level of oocyte nuclear maturation as does pFF alone or pFF with EGF and/or IGF‐I. IGF‐I does not appear to influence nuclear maturation of GCOC. © 1993 Wiley‐Liss, Inc.