This publication is intended as a guide for existing or potential users of ground-water supplies. Included is basic information on factors which affect the occurrence, the quantity and the quality of ground water, a synopsis on well construction, and a discussion of common problems associated with wells and water-supply systems. In addition, the existing Ontario Water Well Regulations are discussed with respect to the well owner and the water-well contractor. It should be stressed that this guide is not intended as a manual on well construction nor a manual on pump installation since both of these operations require considerable background training and experience.