A versatile large-scale batch culture unit has been developed for the growth of plant cell suspension cultures. This unit has been modified to permit of intermittent or continuous renewal of culture medium and, in a modified form, incorporated into open continuous culture systems of the chemostat and turbidostat type. A fully automatic culture sampler has been incorporated into the basic culture unit. The culture systems described have been successfully operated using a cell suspension derived from Acer pseudoplatanus and results are presented demonstrating synchronous growth in batch culture, prolonged logarithmic increasse in cell number under conditions of high aeration and culture medium renewal, and steady states of growth resulting from automatic regulation of the optical density of the cell suspension and from fixed rates of displacement of cell suspension by new medium. The potentialities of the culture systems are discussed in the light of the experimental results presented.