Technical Abstract: Despite being known mainly as mammalian disease agents, Streptococcus iniae and S. agalactiae have become recognized as emerging pathogens of wild and cultured fish. The worldwide economic impact of S. iniae and S. agalactiae to the aquaculture industry is estimated in hundreds of millions annually. This article will focus on the epizootiological aspects of these pathogens in tilapia Oreochromis spp. and other warm-water fish including global distribution, fish hosts susceptibility, disease signs, sample collection, transport and storage for successful survival and isolation, identification by conventional, automated and molecular diagnostic techniques, antibiotic sensitivities, and environmental influences on disease susceptibility. Overall, this talk will chronicle the road from emergence of these piscine pathogens to detection, understanding, treatment and prevention (Klesius et al., this proceedings).