Survey of literature on the therapeutic and prophylactic value of lithium carbonate. The therapeutic value in the treatment of mania has been established beyond doubt; the therapeutic value in depression is doubtful and is inferior to the effect of anti-depressive drugs. An important issue is the effect of lithium prophylaxis of recurrent manie and depressive psychoses. A rapidly growing number of well-designed and controlled studies over many years and many hospitals indicates a real and important prophylactic effect, not only by reducing the number of manic attacks but also of depressive relapses. The problems of complications and toxicity, dosage and control are discussed.