Lithium carbonate was administered to normal controls and to manic-depressive patients under carefully controlled conditions. Particular attention was given to diet. The authors found that lithium clearly affects the metabolism of sodium and calcium and, to some extent, magnesium. Minimal affective and behavioral effects of the lithium were noted by the normal controls. There was some suggestion of abnormality in the circadian (24-hour) rhythm of temperature and some other physiological measurements among the manic-depressive group.