Papillomaviruses are a subfamily of the papovaviridae. They are highly species-specific and can cause squamous epithelial and fibroepithelial tumours in their hosts. Since no efficient system for the propagation of papillomaviruses existed, not much was known about the requirements for virion assembly and the strategies used to invade the host cells. Recent progress in the development of in vitro systems for the generation of papillomavirus-like particles (VLPs) and pseudovirions has allowed to analyse some of the structural features required for capsid assembly, capsid integrity and DNA incorporation into capsids. In addition, in vitro infection assays have been developed to study papillomaviral uptake by eukaryotic cells. This has led to the identification of a candidate receptor protein and of epitopes inducing neutralizing antibodies.