Infertility is estimated to affect one of every five Polish couples in the reproductive age. Antisperm antibodies (ASA) are considered to be the main cause for immunological infertility, but it is still relatively little known about the specific mechanisms that elicit development of auto- and isoim- mune reactions in humans. Antibodies directed to sperm antigens can be detected in serum of men and women, but also in reproductive tract secretions such as seminal fluid, where they can be bound to the sperm surface. Free ASA can be also found in cervical mucus, peritoneal, oviductal and follicular fluids of women. Presence of ASA may impair sperm fertilization capacity through various effects, interfering with pre- as well as post-fertilization stages of the reproductive process. They may affect sperm motility, sperm penetration to cervical mucus, the acrosome reaction, sperm binding to zona pellucida, sperm- oocyte fusion and embryo cleavage. The detailed identification and characterization of the auto- and isoimmune reactive sperm antigens would be useful in understanding the mechanisms underlying the immunological infertility. Moreover, a precise knowledge on the sperm antigens would provide more accurate diagnostic approaches and treatment options.