Sponges (phylum Porifera) branch basally in the metazoan phylogenetic tree. That is why the data on the reproduction must be accumulated and compared between the sponge lineages and eumetazoans in order to understand the early evolution of this processes in animals. The purpose of this chapter is to show the state of knowledge of sponge reproduction. Both gonochorism and hermaphroditism as well as viviparity and oviparity occur in sponges. In spite of absence of the gonads, sexual reproduction includes gametogenesis (spermatogenesis and oogenesis), embryonic development, larval, and postlarval (metamorphosis) morphogenesis. Asexual reproduction may proceed by fragmentation, budding and gemmulogenesis. The influence of factors associated with environmental conditions on sponge reproduction discuss in this paper.