Surface and groundwater quality of Mersin-Tarsus hillside and coastal aquifers extending between Berden and Karakuz was investigated by meanbs of in-situ measurements and chemical analyses during the years 200-2002-2003. Groundwater's temperature, pH and specific electrical conductivity are found to range between 20-26 degrees C, 6.4-8.6 amd 385-6890 microS/cm respectively. In two hotwater wells, temperature, pH and spectific electical conductivity are between 38-40 degrees C, 7.32-7.59 and 10900-12000 microS/cm. Great majority of groundwater samples belongs to Ca-HCO3 facies though MgHCO3 NaHCo3, NaCl, CaSo(4) and Naso(4) type waters were also observes. In considerable number of samples, nitrate exceeds drinking water limits while, limited number of samples posses Fe and Cd above the limits. Seawater intrusion is observed only in a few sites.