SE France is the area the most affected by wildfires, so for a better fire prevention, it is necessary to understand wildfires variation in space and time and to improve the knowledge of their causes. Using the forest fires database Prométhée which gathers all the forest fires of SE France since 1973, the number of fires, their size and causes were investigated during two time periods (1973-1990 and 1991-2010), in three geographical areas of the study area. Two fire sizes were taken into account as the large fires (≥100 ha) represented 1% of the total number of fires but burned 72% of the total area between 1973 and 2010. There was a significant decrease in occurrence and burned area from the first period to the second, except for region 1 in which the number of fires increased. The three regions differed significantly in number of fires and burned areas, region 1 being the most affected. The knowledge of fire causes varied spatially; the proportion of unknown causes being the highest in region 1, and it increased between both periods. Fire causes varied spatially; the main causes were arson in region 1 and negligence during professional activities (especially farm works) in regions 2 and 3. There was also a temporal variation, following the LCLU changes, but also between the seasons. On the whole, the proportions of causes due to arson and to negligence during leisure activities increased between both periods, especially in summer, while that of causes due to professional activities, more frequent from fall to spring, decreased regardless of the region. Large fires were mainly due to arson, except in region 3 where negligence during farm works was the main cause, whereas smaller fires were mainly due to negligence during farm works especially. Before 1991, the main cause differed between regions, ranging from negligence during professional activities (region 3) to arson (region2) and accidental fires in rubbish dump (region 1) but since then, arson is the most frequent cause regardless of the region.