Abstract: Surface and groundwater quality ofMersin-Tarsus hillside and coastal aquifers extending betweenBerdan and Karakuz streams was investigated by means ofin-situ measurements and chemical analysesduring the years 2001-2002-2003. Groundwater`s temperature, pHand specific electrical conductivity arefound to range between 20-26 °C, 6.4-8.6 and 385-6890 microS/cm, respectively. In two hotwater wells,temperature, pH and specific electrical conductivity are between 38-40°C, 7.32-7.59 and 10900-12000microS/cm. Great majority ofgroundwatersamples belongs to Ca-HCO}facies though, MgHC03, NaHC03,NaCl, CaSO4 andNaSO4 type waterswere also observed. In considerable number ofsamples, nitrate exceedsdrinking water limits while, limited number ofsamplesposses Fe and Cd values above the limits. Seawaterintrusion is observed only in a fewsites.