Sperm (spermatozoa and the various secretions of the accessory glands) with its very complex antigenic system is only produced from puberty and thus at a time when the body has already had a for a long time the facility to respond to an antigenic stimulation with an immune reaction. Because of this, the spermatozoa, in contrast to other cells of the organism, are considered as strangers and may behave as auto-antigens. However, the existence of a haemato-testicular barrier, that prevents all contact between the sperm and the immune system must be recognized in man, its rupture has the consequence of formation of anti-spermatozoa antibodies. It is estimated that 5% of cases of sterility are of immunological origin and linked to the presence in man and/or woman of anti-sperm antibodies. The production is greater in man than in women because of the roles, in the first of macrophages and in the second of polynuclear neutrophils in the destruction of the spermatozoa. Anti spermatozoal antibodies play a part in sterility by: Spontaneous agglutination in ejaculation, thus preventing their progression in the female genital tract. Free spermatozoa, charged with antibody are retained at the level of the cervical secretion = SHAKING phenomenon. The anti-spermatozoal antibodies mask some antigens, so preventing penetration of the spermatozoa into the ovule. Contact of spermatozoa with antibody fixed to the uterine tissue is followed by secretion of histamine and this encourages the expulsion of an implanted egg. This is before the existence of: Spontaneous agglutination in ejaculation, Oligospermatosis, Indeterminate cause sterility, Immobilisation of the spermatozoa in the cervical secretion, Failure of repetition.