Elevated concentration of leukocytes in semen has been associated with genital tract infection, poor semen quality and IVF and embryo transfer failure. The world health organization (WHO) defined the threshold value for normal white blood cells (WBCs) in semen as less than one million/ml. There is no consensus for this threshold in different literatures possibly because there is no reliable method to detect and differentiate seminal white blood cells accurately. The aim of this work is to compare the level of seminal leukocytes in cases of idiopathic infertility with normal fertile controls using routine technique, peroxidase technique & flowcytometric evaluation of CD45 monoclonal antibody. Twenty patients with idiopathic infertility for at least two years duration were collected from the outpatient clinic of the Andrology department in Kasr EL-Aini hospital, Cairo University. Ten patients with proven leukocytospermia by routine semen analysis and peroxidase test, and another ten fertile controls with no evidence of leukocytospermia, were also collected. Our results showed that flowcytometry is a simple, reproducible method that enables leukocytes in semen of idiopathic infertility patients to be accurately detected and to identify WBC subpopulations, using a single monoclonal antibody and with no preliminary purification procedures. Patients with idiopathic infertility can be encouraged to quit smoking to improve their semen parameters. The peroxidase test appears to be useful test for screening cases of leukocytospermia. More studies are needed to clarify the biological significance of WBC in semen and their relationship with male infertility.