The cretaceous sandstones of the Beberibe formation are the main aquifeR of the seashore region Olinda-Goiana, State of Pernambuco. The low section corresponds to a semi-confined zone containing corrosive and soft waters while the upper section which is calciferous and partially recovered by a limestone formation, contains hard and more carbonated waters. As the water circulation in the confined zones tends to be nul under non influenced conditions and due to the existence of semi-impermeable sediments, in the vertical direction, there is no significant Iateral escape towards the sea. This hydrogeochemical study indicates that there are no highly salinized waters in these zones, although the vertical eletrical soundings have inclicated, along the seashore, very salinized waters at depth of 30-40 meters. The penetration of salty waters into the continent must be insignificant and limited to the superficial zone submitted to the influence of the tide; the salinity area is reduced to the channels and surroundings, being its influence rapidly limited laterally and vertically. Evidence of sea contamination only occurs in some wells of the intensively exploited area near Olinda, with the rK/rNa ratio being very low and with positive itb values equal or superior to those of sea water. Because of the hydrodynamic characteristics of the aquifer, it seems to be unlikely that the salinity in these wells is due to the horizontal flow of the sea water or vertical descendent circulation through the "aquitard", since these processes occur at very slow rates. On the other hand, penetration of salty water along the well casing or the existence of preferential zones of vertical flows cannot be eliminatedThe cretaceous sandstones of the Beberibe formation are the main aquifeR of the seashore region Olinda-Goiana, State of Pernambuco. The low section corresponds to a semi-confined zone containing corrosive and soft waters while the upper section which is calciferous and partially recovered by a limestone formation, contains hard and more carbonated waters. As the water circulation in the confined zones tends to be nul under non influenced conditions and due to the existence of semi-impermeable sediments, in the vertical direction, there is no significant Iateral escape towards the sea. This hydrogeochemical study indicates that there are no highly salinized waters in these zones, although the vertical eletrical soundings have inclicated, along the seashore, very salinized waters at depth of 30-40 meters. The penetration of salty waters into the continent must be insignificant and limited to the superficial zone submitted to the influence of the tide; the salinity area is reduced to the channels and surroundings, being its influence rapidly limited laterally and vertically. Evidence of sea contamination only occurs in some wells of the intensively exploited area near Olinda, with the rK/rNa ratio being very low and with positive itb values equal or superior to those of sea water. Because of the hydrodynamic characteristics of the aquifer, it seems to be unlikely that the salinity in these wells is due to the horizontal flow of the sea water or vertical descendent circulation through the "aquitard", since these processes occur at very slow rates. On the other hand, penetration of salty water along the well casing or the existence of preferential zones of vertical flows cannot be eliminated