This study was conducted to identify an in vitro culture system that would support intact porcine follicle growth from preantral follicle to antral stages, oocyte maturation, fertilization, and embryonic development; and to evaluate factors that influence porcine preantral follicle growth in vitro. Preantral follicles isolated from prepubertal porcine ovaries were cultured for 4 days in the presence of different concentrations of porcine serum and FSH, and with different numbers of follicles per well. A series of experiments showed that porcine antral follicles can be grown at a high frequency in vitro from healthy preantral follicles with intact theca when cultured in North Carolina State University 23 medium supplemented with 1.5 ng/ml FSH, 7.5% serum, and when cultured with three follicles per well. After 4 days of culture, 68% healthy cumulus-enclosed oocytes from these follicles were obtained, and 51% of the oocytes completed meiotic maturation to the metaphase II stage. Fifty-three percent of the mature oocytes underwent fertilization, 43% of the fertilized oocytes cleaved, and 13% developed to the blastocyst stage. The results show 1) that porcine preantral follicles can grow efficiently to the antral stage using these culture conditions, and 2) that oocytes from in vitro-matured porcine preantral follicles can acquire meiotic competence and undergo fertilization and embryonic development.