The salinity and temperature tolerances of some species of medusae were studied in the laboratory. The results showed the following order of tolerances in diluted seawater: Cirrholovenia tetranema, Clytia cylindrica and Eucheilota duodecimalis > Proboscidactyla ornata and Obelia spp. > Euphysora gracilis, Ectopleura dumortieri, Liriope tetraphylla and Cunina octonaria. In relation to the decrease of temperature, the following results were obtained: Ectopleura dumortieri, Euphysora gracilis, Obelia spp. and Proboscidactyla ornata > Liriope tetraphylla > Cunina octonaria > Clytia cylindrica and Eucheilota duodecimalis. The results obtained in laboratory were discussed in relation to the distribution of the species in nature.