Skin diseases consistently rank third or fourth, and occasionally first, among diseases causing military disability in the humid tropics. Miliaria is one of these common dermatoses. It causes discomfort and sometimes disability and can lead to cutaneous and perhaps constitutional sequelae. Experimental miliaria rubra was produced on approximately 60% of the skin surface of six heatacclimatized volunteers. When examined at one and two weeks after miliaria induction, these volunteers suffered from hypohidrosis without clinically visible miliaria. At these times they were severely disabled by heat and work stress when compared to their own premiliaria performance and to the simultaneous performance of four heat acclimatized controls. These findings raise the question whether certain heat casualties may result from widespread, no longer apparent miliaria and its subsequent longer-lasting hypohidrosis.