From July 1 through July 13, 1993, the heat wave in the eastern United States has been implicated as the direct cause of or a contributing factor to 84 deaths among persons residing in the Philadelphia area. In Philadelphia County, the medical examiner (ME) lists hyperthermia as a contributing factor leading to death if a decedent is elderly or infirm and was exposed to a hot environment. However, reporting of hyperthermia on a death certificate depends on the criteria of individual MEs or coroners. This article describes three case reports of heat-related deaths in other parts of the United States in 1993, summarizes risk factors for this problem, and reviews measures to prevent heat-related illness.