In batch suspension cultures variation occurs in the growth and metabolism of the cells both in space and with time. Viable cell populations of sycamore (Acer pseudoplatanus L.), showing greatly reduced aggregation and more uniform morphology, can be obtained by incorporating enzymes into the culture medium. Such techniques combined with single cell cloning will take us closer to uniformity within the culture. The problem set by the continuous change in the metabolic activities of the cells with time (during the progress of the growth cycle of batch cultures) has been overcome by the use of low-density synchronous cultures and by the establishment of steady states of growth in chemostat cultures. Experimental work with sycamore cell suspensions is described showing (1) the achievement of prolonged cell division synchrony in 4-liter suspension cultures and (2) the conformity of the growth kinetics of cells in chemostat culture to the mathematical model developed by Monod (1950, Ann. Inst. Pasteur (Paris), 79: 390–410) for microorganisms.