The thermal environments of six winter survival shelters with woodburning fires were investigated at Ladd AFB, Alaska, in the winter months of 1954. Ambient temperatures ranged between 0° and -41° F. The survival shelters included a one- and six-man lean-to, two types of paratepees, a willow shelter, and a moss covered shelter. A glass cloth fireplace utilized in the tests proved to be a light-weight and portable substitute for a Yukon stove and allowed a fire to be kindled in an enclosed shelter. The willow shelter, paratepees, and moss covered house provided adequate and similar thermal environments. The lean-tos were inadequate and it is recommended that teaching of their construction be discontinued in the Arctic Survival School. It is further recommended that consideration be given by the Arctic Survival School to the construction of moss covered shelters, as moss mats are abundant in the arctic taiga.