Jellyfish', a group that includes scyphomedusae, hydromedusae, siphonophores and ctenophores, are important zooplankton predatorsthroughout the world's estuaries and oceans. These beautiful creatureshave come to public attention as featured exhibits in aquaria and innews headlines as invaders and as providers of genes used inbiomedical research. Nevertheless, jellyfish are generally consideredto be nuisances because they interfere with human activities bystinging swimmers, clogging power plant intakes and nets of fishermenand fish farms, and competing with fish and eating fish eggs andlarvae. There is concern that environmental changes such as globalwarming, eutrophication, and over-fishing may result in increasedjellyfish populations.The literature reviews and research papers in this volume explore theinteractions between jellyfish and humans. Papers cover the medicalaspects of jellyfish stings, jellyfish as human food and jellyfishfisheries, interactions of jellyfish and fish, effects ofenvironmental changes on jellyfish, effects of introduced ctenophoreson the Black Sea ecosystem, factors causing increases orconcentrations of jellyfish, and others aspects of jellyfish ecology.This is an important reference for students and professional marinebiologists, oceanographers, fishery scientists, and aquarists.