The double-blind controlled studies on lithium carbonate therapy conducted in Japan have demonstrated that there are no significant correlations between clinical effectiveness and serum lithium level in manic patients as well as depressed patients and also that Japanese patients seem to require less lithium carbonate than their U.S. counterparts as an effective therapeutic dose, both in terms of mean maximum dose and serum level. Although any international comparison cannot be fully valid without using transculturally standardized assessment, the data of these studies were examined from the viewpoint of transcultural psychopharmacology and compared to the data from studies in U.S.A.