Heat-related deaths typically occur during summer months. Many of these deaths are preventable. This report describes four cases of heat-related deaths in Los Angeles County, California, during 1999-2000, compares age-, sex-, and race-specific rates in Los Angeles County and the United States during 1979-1998, and summarizes trends in the United States during 1979-1998. Relatives, neighbors, and caretakers of persons at risk for heat-related death should frequently evaluate heat-related hazards, recognize symptoms of heat-related morbidity, and take appropriate preventive action.