White blood cells (WBCs) are present in most human ejaculates, but abnormally high concentration of seminal leukocytes may reflect an underlying pathological condition. The World Health Organization (WHO) has defined leukocytospermia as status of more than $10^6$ WBC/mL of semen. The purpose of this study was firstly, to compare the outcomes between conventional IVF and ICSI in leukocytospermia, and secondly, to investigate whether ICSI may be an alternative treatment for patients with leukocytospermia. Total 121 cycles of conventional IVF and ICSI candidates underwent IVF cycles at PL Infertility Clinic. Semen Parameters including concentration, motility, morphology of spermatozoa and concentration of leukocytes were assessed from the raw ejaculates. There was no difference in sperm concentration, motility and morphology. The rates of fertilization and good embryo development from ICSI were significantly higher than those from conventional IVF in leukocytospermia (63.9% & 48.6%, respectively for ICSI group and 33.4% & 24.1%, respectively for IVF group, p<0.001). The pregnancy rate after ICSI was also higher than that from conventional IVF (34.3% vs 21.6%, p<0.05). These results indicate that the presence of seminal leukocytes ($>1 imes10^6$ WBC/mL of semen) is adversely related with fertilization, embryo development and pregnancy rate. Therefore the measurement of seminal leukocytes in routine semen analysis appears to be of prognostic value with regard to male fertilizing potential. In conclusion, it is suggested that ICSI is an alternative choice of treatment for patients with leukocytospermia.