The most suitable methods of disinfesting clothing and bedding depend upon circumstances, such as the extent and importance of the pest infestation, the numbers to be treated and the facilities available. This paper describes investigations of heat and cold for killing lice which were undertaken with an eye to very different situations, viz., the heat treatment of bedding in London air-raid shelters and the possible use of winter cold in Eastern Europe during post-war relief. Nevertheless, the problems have one thing in common; the inherent difficulty of heat transference through clothing and bedding.