The manual, is divided into four chapters. The first chapter-general theoretical problems-treats underground water and its behaviour as a natural historical process reflecting certain peculiarities attendant upon its development. This is of primary importance for basic regional hydrogeological stations in ensuring proper scientific organization of stationary (permanent) observations.The information contained herein is the result of conclusions drawn from scientific analyses of work conducted for a prolonged period at hydrogeological stations of the Ministry of Geology and Conservation of Mineral Resources of the U.S.S.R. We will add that some of the statements and conclusions are being published bore for the first time and are intended for broad discussion among interested hydrogeologists. Among other things included is a classification of factors determining tho regime of ground wa- ters and their genetic types (types of origin).The present work does not embrace underground water problems as pertaining to the design of various engineering structures, although quite a few of its recommendations may be of value for the purpose.