The purpose of this study was to determine the insulative value of the Navy MK-5 anti-exposure suit and the Air Force CSU4P partial pressure suit in wet and dry cold environments. Human subjects were exposed to both environments while wearing each assembly. Results of these exposures are shown in graphs of skin and rectal temperatures. A discussion of the results is presented. The MK-5 and CSU4P assemblies when used with additional protective equipment may be considered adequate protection for dry still air temperatures of -30 F. The MK-5 and liner is adequate protection for water survival in excess of 8 hours. The CSU4P is adequate water survival protection for periods in excess of two hours. Additional insulation will increase the capability of either assembly during water immersion.