The main concerns in dealing with aquifer contamination by ethanol-amended gasoline are focused on the complex physical, chemical and biological interactions between gasoline constituents and ethanol, which may limit the selection of proper environmental restoration technologies. To evaluate the impact of ethanol in gasohol spills, studies are being performed by Petrobras in association with the Federal University of Santa Catarina in Florianópolis, SC, Brazil. This presentation shows results of long-term controlled release experiments (natural attenuation and bioremediation with nitrate), performed in a sandy aquifer with gasoline containing 24% ethanol since 1998. New natural attenuation studies with diesel and biodiesel mixtures (B20) as well as a risk assessment model that includes the effects of ethanol will also be presented.