The reproductive system is a system of organs within an organism which work together for the purpose of reproduction. Reproductive system is a vital system for any animal. On the other hand, the process of the maintenance of the continuity of generation using such organ systems is known as reproduction. Adult male and female members of every animal engage themselves in reproductive activities to produce their off-springs. But the reproductive system not only performs reproduction rather it shows the evolutionary relationship among animals. This book talks about the comparative dimensions of the reproductive systems of 3 species of fishes (Hypophthalmichthys molitrix (Valenciennes, 1844), Labeo rohita (Hamilton, 1822) and Puntius sophore (Hamilton, 1822)) of the Family- Cyprinidae to establish that particular relationship.