Uterine leiomyomas are the most common benign uterine tumors in the women of reproductive age. Previous studies have suggested that uterine leiomyomas are monoclonal tumors derived from a single neoplastic myometrial cell. However, the neoplastic transformation of myometrium to leiomyomas remains to be elucidated. The classical cadherins are a gene family of integral membrane glycoproteins that mediate calcium-dependent cell–cell adhesion in a homophilic manner. These cell adhesion molecules (CAMs) have been shown to play pivotal roles in tumorigenesis. Catenins are intracellular proteins that link the cytoplasmic domains of the cadherins to the cytoskeletons to promote the biological functions of these CAMs. In this study, we compared the expression of E-, N-, and P-cadherins and α-, β-, and γ-catenins in the uterine leiomyomas and the counterparts of normal myometrium of the same patients by using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. Of these, E-cadherin (E-cad) was not detected in both uterine leiomyomas and myometrium, P-cadherin (P-cad) was similarly expressed in these two tissues, but N-cadherin (N-cad) mRNA and protein expression levels in uterine leiomyomas were significantly greater than those observed in the myometrium. Catenins were not differentially expressed in uterine myometrium and leiomyomas. The overexpression of N-cad in uterine leiomyomas suggests that this CAM may play a central role in the development of uterine leiomyomas. Mol. Reprod. Dev. 64: 172–178, 2003. © 2003 Wiley-Liss, Inc.