Frozen semen obtained from 5 different Korean Native Cattle were used for in vitro fertilization of oocytes. The proportions(3∼11%) of oocytes penetrated in the basic medium with 13.9 mM glucose were very low in different semen. However, the penetration rates of oocytes in the presence of caffeine and heparin increased to 68∼84%. The proportions(10∼52%) of oocytes penetrated in the presence of caffeine alone were low at various glucose concentrations(0∼27.8 mM). In the medium with heparin, significantly(P<0.05 at least) higher penetration rate was obtained in the absence(94%) than in the presence(28∼45%) of 0∼27.8 mM glucose concentrations. The medium with caffeine and heparin, however, produced similar penetration rates(84∼97%) regardless of the various glucose concentrations.