The kinetic growth of unialga Chlorella vulgaris was investigated in mixed-culture fed-batch chemostat reactors, with special reference to temperature and pH. The experiments were carried out at 10 degrees C to 40 degrees C, pH was controlled from 3.0 to 11.5 in a series of reactors, and glucose at a concentration of 75 mg/L was fed as the sole source of organic carbon. The maximum growth rate of 0.50 day(-1) was obtained at pH of about 6.31 to 6.84, and the optimum temperature was 32.4 degrees C. The activation energy of the growth-limiting reaction and the enthalpy change for the enzyme-inactivation reaction were 24.5 and 253.36 kJ/mole, respectively. The saturation constants for hydrogen ion, K-H, and hydroxyl ion, K-OH, were temperature-dependent. At temperatures below optimum, K-H increased when temperature increased, but K-OH decreased. Above the optimum temperature, K-H decreased and K-OH increased with temperature.