E-cadherin is a calcium-dependent, intercellular adhesion molecule that is specifically expressed in epithelial tissues and plays an important role in maintaining epithelial stability. E-cadherin is widely regarded as a prognostic marker in many types of human cancers. The inactivation of the E-cadherin gene is linked to increased potential for tumor invasiveness and distant metastasis. We previously demonstrated reduced expression of E-cadherin protein immunohistochemically in invasive squamous cell carcinomas of the skin as compared with adjacent normal skin. An epigenetic alteration in association with promoter hypermethylation is one important mechanism of gene silencing. In the present study, we analyze the E-cadherin gene promoter hypermethylation in preneoplastic and neoplastic skin lesions to determine whether epigenetic alteration of the E-cadherin gene also plays an important role in cutaneous squamous carcinogenesis. A total of 33 cases was examined for evidence of E-cadherin promoter hypermethylation, and these consist of nine cases of spongiotic dermatitis as nonneoplastic skin control, nine cases of actinic keratosis, eight cases of squamous cell carcinoma in situ, and seven cases of invasive squamous cell carcinoma. Promoter hypermethylation of the E-cadherin gene was detected in 6 of 7 cases (85%) of invasive squamous cell carcinoma, 4 of 8 cases (50%) of squamous cell carcinoma in situ, 4 of 9 cases (44%) of actinic keratosis, and 2 of 9 cases (22%) of nonneoplastic skin. We conclude that E-cadherin promoter hypermethylation occurs frequently and may represent an important mechanism of E-cadherin inactivation in cutaneous preneoplastic and neoplastic lesions. The frequencies of E-cadherin promoter hypermethylation appear to be correlated with more advanced stage of squamous carcinogenesis in skin.