Public health is severely affected by inadequate water supplies in Micronesia, a vast island-dotted area of the Western Pacific that had been held in trust by the United States from the end of World War II until recently. Many residents of the islands rely on catchment of rainwater for supplies; others are served by deteriorating systems carrying untreated water. The difficulties of coping with water demand and upgrading water service in such a remote and varied tropical location are discussed. Includes 3 references, table, figure.