Experiments carried out with hepatocytes entrapped in alginate gel particles with a cell density of about 10(7) cells ml(-1) showed an oxygen consumption rate of about 2.2x10(-16) mol cell(-1) s(-1). Under these conditions, no inner anoxic core is present in 1.8 mm diameter beads. From these data, the maximum bead size consistent with non-critical O-2 concentration at the bead center has been evaluated for different cell densities and O-2 concentrations in the medium.