A spinner culture system for the growth of tissue cells in fluid suspension has been described. Actively proliferating mammalian cell suspensions, in volumes of 25 to 400 ml have been established utilizing the prototype “L” cell. Similar, although less extensive, investigations have been conducted with strain HeLa. A 300 to 400 ml “L” cell spinner culture has been continuously maintained for the last 5 months. It is suggested that the described submerged culture system provides a more quantitative tool for investigations relating to the response of the mammalian cell to infectious or pharmacologic agents.