To investigate the effect of heparin on sperm capacitation. The acrosome reaction of bovine sperm which were incubated in mTALP containing heparin and the in vitro development of bovine follicular oocytes which were cocultured with heparin-treated sperm were evaluated, and the resutls were as follows : 1. When bovine fresh sperm were incubated in mTALP solution containing 0, 5, 10 and 25$mu extrm{g}$/ml heparin for 15 to 840 minutes, there was no significant difference between motilies of heparin-treated sperm and untreated sperm, but the acrosome-reaction rate of heparin-treated sperm was significantly higher than that of untreated sperm. Moreover the acrosome reaction rate of was sperm treated with heparin was significantly increased after incubating for 15 minutes. 2. When fresh sperm were incubated in mTALP solution containing 10$mu extrm{g}$/ml heparn for 840 minutes, the motility of sper incubated for 840 minutes was lower than those of sperm incubated for 0, 15, 60 and 120 minutes, but the acrosome-reaction rate of sperm incubated for 840 minutes was higher than those of the others. 3. When frozen-sperm were incubated in mTALP solution containing 10$mu extrm{g}$/ml heparin for 120 minutes, the acrosome reaction rate of sperm was significantly increased after incubating for 15 minutes. 4. When fresh sperm treated with heparin were cocultured with bovine follicular oocytes, 16.7 to 23.7% of the oocytes were developed to 2-8 cell stage.