The development of porcine oocytes from large (3.1-8.0 mm in diameter) or small (<3.1 mm) follicles was examined after maturation culture in medium containing porcine follicular fluid (pFF). Large follicles yielded larger (256 microm v. 221 microm; P<0.05) cumulus-oocyte complexes and more (22 v. 14%) morphologically normal oocytes than small follicles (Experiment 1). In Experiments 2-4, maturation media supplemented with mixed pFF (10%) from small and large follicles was used. More oocytes from large follicles matured (58% v. 91%), formed pronuclei (81% v. 90%) and developed to the blastocyst stage (2% v. 10%) than oocytes from small follicles. In Experiments 5-7, the effects of pFF collected from either small or large follicles on oocyte development were examined. Regardless of the source of oocytes, large-follicle-derived pFF more significantly enhanced preimplantation development than did small-follicle-derived pFF. The highest rate of blastocyst formation (16%) was found when oocytes from large follicles were cultured in maturation medium containing large-follicle-derived pFF. These results suggest that oocytes from large follicles have greater developmental potential than oocytes from small follicles, and that the origin of pFF, which is added to the maturation media, might be an important factor for improving in vitro development of porcine oocytes.