167-172Ground water from Cuddalore to Puduchatiram collected in two seasons, were chemically analysed for various parameters, so as to provide a baseline data. Chemical weathering plays a major role in controlling the water chemistry in this region. The majority of the samples fall in Na+K, Ca+Mg and SO4+Cl geochemical types. Ground water quality is good for all purpose except at few locations in inland region and coastal tracts. Areas seriously contaminated by seawater intrusion have been identified