Infertility related issues are one of the most distressing and depressing facts of newly married couples. They struggle for years together, investing in lot many investigations advised by treating physicians without any results. Such are the cases where male factors are mainly responsible, the causes you thought could be beyond that. Although infertility was believed to originate from female abnormalities, recent discoveries have revealed that as many as 50% of cases stem from male-factor defects, with no identifiable cause in 25% of infertile men. Male infertility presents an vexing problem for men all over the world.This book provides the data on protein analysis of sperms of oligozoospermic males and when compared with that of normozoospemic sperm proteins, a definite difference was found. The same happened with sialic acid contents of the sperm. Role of these factors in fertility is much more than thought of. The measurements of these parameters could be useful in establishing a new understanding of molecular basis of male infertility. Increasingly, genetic defects could be identified in infertile men, as well.