Pyospermia is found on the semen analysis of up to 23% of men who are being investigated for infertility. The presence of significant numbers of white blood cells in the semen is correlated with poorer sperm parameters and diminished fertility. It is not known if these changes in sperm function are due to the white blood cells or to an underlying problem that may cause both pyospermia and altered sperm function. It is often assumed that pyospermia is an indication of an underlying genitourinary infection. However, studies have not shown an association between bacteria growing in reproductive tract fluids (semen, urine and expressed prostatic secretions) and pyospermia. Despite this, treating these patients with different antibiotics regimens appears to reduce temporarily the white blood cell count in the semen and improve the fertility rates. Well-controlled studies are needed to determine the role of antibiotics in the treatment of this significant cause of male infertility.