Semen analysis is still today a fundamental stage in male fertility diagnosis. In fact it's essential to evaluate didimal functional state and particularly the sperm genesis. But a semen analysis with normal parameters does not assure male fertility. Except the cases of azoospermia it does not distinguishes fertile from infertile patients, but when the sperm quality decrease, the pregnancy rate also decrease but rarely touch zero. Reliability of the analysis depends on the experience and on the analyst's ability who has to give an opinion about fundamental parameters like motility and sperm morphology. It is most correct to talk about semen analysis instead of semen examination because is possible to obtain not only number and quality of spermatozoa but also hormonal, immunological, bacteriological, cytogenetic, biomolecular data. Furthermore in the last ten years a lot of functional tests have been perfected, able to value accurately the integrity of some spermatozoa's "functional compartments" like membrane, acrosoma, DNA, nuclear proteins but these examinations have been considered at level assessment only for select cases. Semen analysis remains therefore a fundamental examinations in the study of male infertility even if rarely it is able to express definitive trials about infertility. In fact this always represents a couple problem, particularly of the couple in study.