Research encompassed two broad areas of investigation: first, a study of chemical constituents in potable ground water; and second, types and problems of severe contamination that render ground water unsatisfactory for human consumption in Massachusetts. Knowledge of the nature of chemical constituents in potable ground water and their areal distribution is valuable in planning future programs of water development. The study indicates that most public ground-water supplies in Massachusetts have a low pH and appreciable amounts of iron and manganese. The study further indicates that areas of ground-water discharge generally have greater amounts of iron, manganese, and low pH than the areas of ground-water recharge. The increase in chloride concentration is also discussed.