Integrins are cell surface adhesion molecules that regulate normal cellular interactions; aberrant integrin expression is believed to play a role in tumour invasion and metastasis. The αv subunit is capable of forming heterodimers with several β subunits but not all the heterodimers expressed in oral epithelium have been investigated. We have examined the distribution of αv integrins in normal buccal mucosa and seventeen oral squamous cell carcinomas. Antibodies to the αv subunit and αvβ5 heterodimer stained normal epithelium, with strong expression in the basal layers and weaker staining in the more superficial layers. The β3 and β6 subunits were not expressed in normal epithelium. Anti-αv and anti-αvβ5 antibodies stained all the squamous cell carcinomas, but the pattern of expression was variable both within and between tumours. Poorly differentiated tumours showed the weakest staining and often had areas showing loss of expression. β6, was expressed in all of the carcinomas, indicating new expression of the αvβ6 integrin in malignant oral epithelium. These results suggest that alterations in αv integrins may contribute to the behaviour of malignant epithelium and that αvβ6 expression may play a role in tumour progression.