Efficacy of lithium therapy in mania is attested to by several investigators. Among the reports are two of double-blind studies which present evidence that the lithium ion has a pronounced influence in terminating episodes of mania.1,2 The mode of action is unknown. Some investigators using lithium therapy for the treatment of mania have noted that manic patients tend to excrete a smaller percentage of a given dose of lithium than do controls. Gershon et al3 noted that manic patients excreted less than 20% of lithium given in the first 24 hours of the therapy, whereas normal patients excreted between 50% to 70% in this period. The control and manic groups received different doses of lithium, however. The observation that manic patients appear to excrete relatively small amounts of lithium during the initial phase of therapy, coupled with the report that a sudden increase in the amount excreted occurs