GSK-3beta codes for an enzyme which is a target for the action of mood stabilizers, lithium and possibly of valproic acid. The relationship between the polymorphisms (SNPs) of GSK-3beta-50T/C and -1727A/T and the effect of lithium was studied among 29 Japanese bipolar patients. It was shown that GSK-3beta-50T/C may be linked with the effect of lithium treatment. There is a significantly higher T-allele frequency in the lithium responders than non-responders (df = 1, chi2 = 6.971, 0.01 > P > 0.001; Yates' continuity correction). However, there is not a significant relationship between the polymorphisms of GSK-3beta-1727A/T and the effect of lithium treatment.