Pesticides use represents a great environmental risk with high economic cost. The objective of this study is to investigate groundwater contamination risk in a small watershed in northeastern Pará State, Brazil, coupling remote sensing, GIS techniques, and simulations. We have confirmed a high risk exposure to contamination by Dimethoate in 67.76 ha, which represents 1.67% of the total watershed area. According to these analyses, Dimethoate has the potential to reach 12.96 m depth in the soil. The groundwater in the study area has a high risk of exposure to contamination by this pesticide, as the water table depth ranges from 1.5 to 13.0 meters. The shallow water table together with soil and geological characteristics increases the potential risk of contamination of groundwater.2007