We wish to call attention to an unusual eruption which occurred among the military personnel in the Southwest Pacific area. The affected persons were members of the Australian and American forces whose stay in the tropics ranged from two to sixteen months. The first patient was seen in October 1943. The number seen by us has steadily increased to 47 at the time of this writing. Some patients have been under constant observation and study; others were observed for only relatively short periods. New cases are still developing, and the study is continuing. Many physicians in the Southwest Pacific area have cooperated by exchanging information and by allowing us to observe patients who presented the eruption on which we are reporting. The syndrome invariably began with an initial eruption which varied widely in different persons. This early eruption mimicked such common dermatoses as heat rash, fungous infection, eczema,