Infections of the male genitourinary tract may contribute to infertility by adversely affecting sperm function, causing anatomical obstruction or initiating a leukocyte response. The majority of infertile males are asymptomatic, and the significance and the criteria for the diagnosis of a genital tract infection are controversial. The evaluation for a genital tract infection focuses on urine and semen cultures as well as on the accurate quantitation of seminal leukocytes. An elevated seminal leukocyte count, pyospermia, can be associated with male infertility and may reflect an infectious or inflammatory disorder. In addition, the role of specific genital tract infections such as chlamydiosis, gonorrhea, ureaplasma and trichomoniasis and their possible association with male infertility is addressed.