Lithuanian health resorts are national resources of this country. Body hardening, health promotion, disease prevention and rehabilitation by means of applying natural factors are linked for centuries with the names of health resorts such as Druskininkai and Birstonas. The effect of natural factors is multiplex and depends on many parameters the study of which in concrete health resorts is indispensable in order to individualize the treatment at the health resorts and avoid undesirable side effects. As the contingent of the patients being referred to the sanatoria is changing--the number of severe patients after acute disorders and traumas is increasing constantly--the need of such studies becomes relevant. However, after renewal of independence of Lithuania in 1990, the policy of health resort development on the national scale has not been carried out yet. Besides, the number of localities that aim for becoming health resorts is increasing, however, such localities often do not meet the required criteria. The article reviews the status of health resorts and their localities together with their regulations in Lithuania, their development, specificity, the effects of the health resort natural factors (climatotherapy, balneotherapy, pelotherapy) on the healthy body and patients. The data are presented on the development of research studies concerning health resorts and main trends of health resort medicine: health promotion, prevention of disorders, early health resort rehabilitation, health resort tourism, treatment and health resort etiology. Possibilities of revival of studies concerning the effects of health resort factors on the rehabilities are discussed.