Groundwater quality and aquifer hydrogeochemistry were investigated in a suburban area of the city of Niteroi where domestic water supply is mainly from this source. Samples of water from deep wells, shallow wells and springs were analysed for parameters indicative of aquifer geology and hydrology: conductivity, alkalinity, HCO3 −, Cl−, Na, Fe, silica, Ca, Mg, K and Mn, and those indicative of contamination: the first five of the preceding list, plus: sulphate, ammonia, nitrate and phosphate. Evidence of contamination by domestic sewage and salinization of waters were shown to occur in a localized manner. The occurrence of reduced iron in well waters was generalized. Indices of vulnera-bility of the aquifers of various sub-areas are presented.