The solubility of CO2 in milk was studied at temperatures of 25, 38 and 50 degrees C and at pressures up to 6.9 MPa using a static method with an accuracy of 5%. These data are important for the design and control of processes which use CO2 for precipitation of casein from milk. The solubility of CO2 in milk was found to increase with pressure and decrease with increasing temperature - a trend similar to that observed for the solubility of CO2 in water. At 25 degrees C, the solubility of CO2 in milk was less than the solubility in water over the entire pressure range studied. Precipitation of casein was not observed. At 38 degrees C and 50 degrees C and pressures greater than 5.5 MPa, complete precipitation of casein from milk was observed? and the solubility of CO2 in milk was approximately the same as that in water. This indicates that casein destabilization is accompanied by an increase in water available for dissolution of CO2.