The growth inhibitory effect of 50 kPa (0.5 atm) CO2was tested forPseudomonas fragiin the temperature range 5–35 °C and of 101 kPa (1 atm) CO2onBacillus cereusin the range 18–46 °C. The maximum specific growth rate (μmax) ofP.fragiin air (pH 6.7) was 0.44 h−1at 35C, 0.66 h−1at 30 °C, and 0.078 h−1at 5 °C. In 50 kPa of CO2in air the relative inhibition of the growth rate was about 30% at 35 °C, 50% at 30 °C, and 90% at 5 °C. Thus, the inhibitory effect of CO2successively increased with decreasing temperature, an effect which was explained by the increasing solubility of CO2with decreasing temperature. The anaerobic growth ofB.cereus(101 kPa N2) was optimal at 40 °C and stopped at temperatures below 18 °C and above 46 °C. The relative inhibitory effect of 101 kPa CO2at the optimum growth temperature was about 40%; this increased to 100% near the maximum and minimum growth temperatures. The growth inhibitory effect of reduced temperature (below optimum) and CO2onB.cereuswas larger than that expected from the increased solubility of CO2at lower temperatures.