Remote-sensing techniques were employed for evaluating the hydro-geological conditions of southern districts of Tamil Nadu, India, in two phases. In the first phase a satellite remote-sensing survey was carried out during 1977-1979. This was followed by systematic groundwater investigations in the above area (phase II). Detailed studies such as aerial photo-interpretation, field investigations and ground data collection were made in four selected test sites to confirm the findings of the phase 1 regional study. The above-mentioned two-phase study provided quicker and more reliable hydrogeological information for rapid groundwater development.