Connecticut has a supply of ground water, most of it of good quality, which is largely undeveloped, and much of which would lend itself to industrial and other uses. Ground water is available in small quantities in nearly all parts of the State, and in moderate to large quantities in many areas, chiefly along the major stream. However, specific and detailed information on the ground water is available in report form for relatively few specific localities and areas. Definitive investigations of the occurrence, general availability, quality, and quality of ground water in Connecticut are being made under cooperative agreements between the State Water Commission and the U.S. Geological Survey; and some progress has been made. Generalized information of a reconnaissance nature is shown on plate 1, which gives areas of estimated moderate to large yields, delineated on the basis of currently available data, and shows the locations of wells for which records are given in tables 1 and 2. Some specific information on particular areas is available in the open files of the agencies cooperating in the investigations.