Aim of this work is to assess the effect of some environmental factors on road accident severity in Tuscany (Italy). ISTAT data on road accidents occurred in Tuscany in 1991-2003 (228,833 accidents) have been analysed, considering the following variables: road type and characteristics, population density in the municipality where the accident occurred, presence of Emergency Medical Services (EMSs) in the municipality, distance between the municipality and the nearest EMS, according to 3 different criteria. The effect of each variable in accident severity (fatal vs not fatal) was assessed through logistic regression analysis. The results confirm the role of structural and environmental factors in influencing accident severity, in particular population density, location on the road and road type, while the effectiveness in preventing serious consequences due to distance from EMS is limited to the municipalities very close to hospitals.