The possible phase of Venus cloud particles has been experimentally studied. Carbon dioxide gas of 0.83 atm held in a uniform temperature mixing cloud chamber was used as a simulated Venus atmosphere at the condensation level. The ice nucleating behavior of some artificial and natural ice nuclei were tested. The heterogenous and homogeneous ice nucleation temperatures in the CO2 atmosphere were found to be 0.5–1.0C lower than those in air. The formed ice crystals showed no appreciable difference in comparison with those found in air. The results indicated that at temperatures < −38.5C the condensate in Venus atmosphere is likely to be ice crystals and above that temperature it can be either supercooled aqueous CO2 solution or ice crystals, depending on the availability of natural ice nuclei.