Tuberous sclerosis (TSC) is an autosomal dominantly inherited disease affecting 1 in 6000 individuals. The TSC gene products, hamartin and tuberin, form a complex, of which tuberin is assumed to be the functional component being involved in a wide variety of different cellular processes. Tuberin has been demonstrated to be localized to both, the cytoplasm and the nucleus. The cytoplasmic/nuclear localization of tuberin is known to be regulated by the serine/threonine protein kinase Akt. Akt also regulates the cytoplasmic/nuclear localization of the cyclin-dependent kinase inhibitor p27. In this study the localization of these two Akt-regulated proteins was analysed in different cell lines.