Background：β -catenin muations were reported to play a causal role in the development of pilomatricomas. In a recent study in Caucasians, 75% of pilomatricomas had β -catenin mutations. Objective：We investigated the causal role of β -catenin gene mutations in pilomatricomas of Koreans. Methods：This study included 20 formalin-fixed, paraffin-embedded pilomatricomas in Koreans. Basophilic nucleated tumor cells were microdissected and, as normal controls, infiltrating inflammatory lymphocytes were microdissected from the same histologic specimens. Sequencing analysis of exon 3 of the β -catenin gene (CTNNB1) was performed. Immunostaining for β -catenin and Lef-1 was performed by the avidin-biotin-peroxidase method. Results：Sequencing analysis found missense mutations (S37Y, S37C, S33C, S33F, and S37F) in CTNNB1 in 6 samples (30%) of 20 pilomatricomas. All pilomatricomas revealed intense expression of nuclear Lef-1 and nuclear and cytoplasmic β -catenin. Conclusion：Frequencies of β -catenin mutations were lower in our study compared with the results in Caucasians. The immunohistochemical results suggest the abnormalities in Wnt-wingless pathway resulting in stabilization or constitutive expression of β -catenin, but the absence of CTNNB1 mutations in 70% of our cases suggests adenomatous polyposis coli gene inactivation, or the involvement of other components of the Wnt-wingless pathway. (Korean J Dermatol 2002;40(1)：14~18)