Besides its well established role in development and tumorogenesis, nuclear translocation of beta-catenin has also been suggested to play a role in adult brain physiology and pathology. However, nuclear localization of beta-catenin has never been observed in adult brain tissue. Immunohistochemical analysis of beta-catenin distribution in the adult mouse brain revealed nuclear localization exclusively in the whole thalamus with the exception of the reticular nucleus. To investigate whether differences in the level of beta-catenin or GSK-3beta (the enzyme that targets it for degradation by the proteasome) might account for the differential localization in thalamus we performed Western analysis of various brain tissues. The beta-catenin/GSK-3beta ratio was higher in thalamus than in the rest of the brain, suggesting a key role of GSK-3beta in this phenomenon.