The combination of the acid-alkali method and eletrophoresis for X-and Y-sperm separation of boar semen was performed We used lactic acid and sodium bicarbonate in acid-alkali method, and electrophoresed at 2.5V and 200 μA. The results obtained were summarized as follows : 1. The frequency of appearance of B-body from alkali treatment of whole semen was significantly higher than that from acid treatment. 2. The frequency of appearance of B-body from alkali treatment at the anode electrode was significantly higher compared with that from acid treatment at the same electrode, while that from acid treatment at the cathode was slightly higher than that from alkali treatment at the same electrode. 3. According to time of treatment, Appearance of B-body from alkali treatment at the anode after electrophonesis was decreased, and the result from acid treatment at the same condition was the opposite, while appearance of B-body from alkali treatment at the cathode after electrophoresis was not changed and that from acid treatment at the same condition was increased. 4. Appearance of B-body from alkali treatment at the anode for 5-10minutes showed the most useful result which was higher than the result (51.9%) from electrophoresis alone by 3 %.