The science of hydrogeology has grown remarkably. Especially, the hydrogeological studies pertaining to the hard rock terrain of many parts of the world have behind. But, now wide attention has been undertaken by geologists all over the world. Water is an essential commodity to mankind. Water was one of the most prized natural resources in the olden times and occupied a prominent position amongst the pagan gods. Tremendous quantities of water are stored in the earth's crust. So, a quite lot of water geochemical investigations have been carried out all over the world. Despite a quite lot of water chemical investigations that have been carried out in the crystalline hard rock terrain of the country, limited attempts have been made previously to assess the groundwater quality in the hard rock terrain of the Pandalgudi aquifer. Keeping with this aim in mind, an attempt has been made in this Ph.D. research work in and around the Pandalgudi region to assess the groundwater quality.