Previously assumed to be monogamous, the mating system of schistosomes has been the subject of some debate since recent findings have shown that change of mate can occur among these parasites. Here, Louis-Albert Tchuem Tchuenté, Vaughan R. Southgate, Claude Combes and Joseph Jourdane review progress made in the understanding of the mating behaviour of schistosomes, and highlight the importance of mating systems in the dynamics of natural transmission of schistosomiasis.