Summary. Fourteen mammalian cell strains were studied in the 'stirrer culture'. Fair to excellent growth wm obtained with twelve of these strains while two strains failed to show evidence of proliferation. Growth curves, maximal population densities, and recovery following subculture of various cell strains, cultivated in this system, were described. Factors effecting the growth of cells under these conditions were outlined. Growth of cells in methods other than the 'stirrer culture' were reported. The practical importance of fluid suspension culture of mammalian cells, the potentialities and the problems involved in scaling such cultures to industrial size were discussed.