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 alpha v subunit is capable of forming heterodimers with several beta subunits but not all the heterodimers expressed in oral epithelium have been investigated. We have examined the distribution of alpha v integrins in normal buccal mucosa and seventeen oral squamous cell carcinomas. Antibodies to the alpha v subunit and alpha v beta 5 heterodimer stained normal epithelium, with strong expression in the basal layers and weaker staining in the more superficial layers. The beta 3 and beta 6 subunits were not expressed in normal epithelium. Anti-alpha v and anti-alpha v beta 5 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. beta 6 was expressed in all of the carcinomas, indicating new expression of the alpha v beta 6 integrin in malignant oral epithelium. These results suggest that alterations in alpha v integrins may contribute to the behaviour of malignant epithelium and that alpha v beta 6 expression may play a role in tumour progression.