Human and mouse LHX6 share more than 95% amino acid homology. Northern blot analysis detected high expression of Lhx6 in embryonic mouse brain, much lower expression in adult mouse brain, and no expression in any other tissue examined. RT-PCR detected peak expression of the Lhx6.1a variant at postnatal day 2.0 (P2.0), and the expression remained high in adult animals. Expression of the Lhx6.1b variant was abundant from E18.5 to P2.0 and decreased at P14.0 through adulthood. In situ hybridization revealed dynamic expression of Lhx6 during mouse brain development. At E9.5, Lhx6 was expressed in the preoptic area, the hypothalamic region, and the first branchial arch. By P1.0, expression had spread to the cortex and hippocampus. In nonneuronal tissues, Lhx6 was localized at P1.0 in the primordial upper and lower molar teeth.