During the second half of June 2005, parts of mainland France experienced a heat wave. According to Météo-France, this episode was exceptional for the month of June due to the temperatures reached (the daily heat index¹ was 25.8°C on June 28, 2005, the hottest day in June since 1950) and its duration. In eight French regions, the pre-alert (level 2) and alert (level 3) levels of the National Heatwave Plan (PNC) were triggered between the 20th and 30th of that month. The Rhône-Alpes region was the hardest hit, with eight departments affected, four of which were placed at level 3 for at least three consecutive days. The objective of this study is to assess the health impact of the June 2005 heat wave in the departments actually affected by extreme heat or placed at level 3 of the PNC. (Introduction)