erm cell development in mammalian gametogenesis involves a complex sequence of events regulated by a large variety of molecules. Although hormones have been always considered the primary regulators of gametogenesis, it is now well established that growth factors (GFs) in concert and against or in some case autonomously of hormones, may control or modulate directly or indirectly many, if not all, of the processes of germ cell development. A number of GFs have been identified produced by gonadal somatic cells and germ cells acting locally to regulate gametogenesis by autocrine and paracrine fashion. Bi-directional communication between gonadal somatic cells and germ cells is critical for gonad function and fertility. Increasing body of evidence has led to the proposition that several GFs are important mediators of such communication and crucial in controlling and determining female and male fertility. In the present review, we will mainly focus on GFs acting directly on female and male germ cells and on those produced by the germ cells themselves.