For several years, many physicians and reproductive researcher did focus in their search for fertility problem on female partner, and only few of them are aware of the scientific implication of accurate assessment of male partner in any infertility case. The understanding of male infertility requires adequate knowledge of the male reproductive system functions which represents the key for appropriate diagnostic method. The major goal of this book is to provide substantial scientific data on the risk factors to male infertility. It results demonstrated the possible role of man aging, presence of urogenital tract infection, and smoking habit in the etiology of male infertility. In addition, it clarified the limited value of traditional semen analysis in comparison to the new molecular techniques and suggests the need to expand research on male infertility.