Verrucous carcinoma of the anus is a distinct and rare variant of well-differentiated squamous cell carcinoma. A case of anal verrucous carcinoma in a 35 year old man was studied by light microscopy and in situ DNA hybridization. Human papillomavirus (HPV) type 16 DNA sequences were demonstrated in the tumour cells, as well as in cells showing koilocytotic and dyskeratotic changes. The possible viral (HPV) aetiology of verrucous carcinoma is considered with a review of the previous literature.