Human papillomaviruses (HPVs) appear to play a role in the etiology of the vast majority of virus-associated human malignancies. Studies of viral gene expression in carcinomas suggest the importance of two HPV encoded proteins, E6 and E7, in malignant development and these proteins have been shown to encode transforming and immortalising activities. The two proteins show some functional resemblance to the transforming proteins of other small DNA tumour viruses such as adenovirus and SV40. Recent evidence suggests that one important function of these virus-encoded proteins is binding the products of the cellular tumour suppressor genes RB and p53, revealing an exciting link between oncogenes and anti-oncogenes.