Human papillomavirus-like particles (VLPs), self-assembled after high level expression of the papillomavirus L1 virion capsid protein in non-mammalian cells, are attractive candidates for a subunit vaccine to prevent genital HPV infection and the subsequent development of cervical cancer. In animal studies, purified VLPs induce high titers of antibodies against conformational type specific L1 epitopes. These antibodies neutralize homologous virions in in-vitro assays and protect against experimental challenge in several animal models. The encouraging results in animals justify the initiation of human trials of HPV VLP-based vaccines. Factors to be considered when designing these trials are discussed.