Leukocytospermia is a most common cause of male infertility, but the distribution, origin and role of leukocytes in semen are still controversial. Some reports on leukocytospermia have indicated its negative effects on semen parameters and even in vitro fertilization (IVF). Recent literature has made it clear that the most deleterious effect of leukocytospermia is that the increased reactive oxygen species (ROS) may cause sperm damage, leading to significantly increased male infertility. The treatment and prevention of leukocytospermia have been proven of help for improving semen parameters.