Some questions of the long-term lithium treatment of affective disorders are discussed based on a statistical analysis of 140 patients. The overall results do not differ from those published elsewhere. Even after 4 years of treatment the number of symptom-free female cases is still increasing and goes beyond 50 %, while another 25 % show only subclinical phases. In men the 4-year results are not so favourable and in the fourth to sixth year they are slightly worse. The difference in therapeutic effects between recurrent unipolar and circular depression is only apparent in men. The prophylaxis of relapses of mania is less successful than that of depressions in both sexes. Changes in the course of the illness, in the general condition of the patient and in the endogenous rhythmicity occur mainly in the beginning of lithium therapy, and are probably slightly more frequent than those associated with other psychotropic drugs. The incidence of side effects is somewhat lower after several years of lithium treatment than in the early stages. A form of an organic psychosyndrome appearing during long-term lithium therapy is discussed.