A simple, reliable culture system for keratinocytes from anogenital warts is described. Using this technique we found that it was possible to produce multiple confluent keratinocyte cultures from two-thirds of the surgically-excised anogenital wart specimens received in our laboratory. Some morphological and cultural differences between these cells and normal keratinocytes derived from neonatal foreskins were observed, although there was no evidence that wart-derived keratinocytes were 'transformed'. The cultures were tested for evidence of HPV-DNA replication using 32P-labelled HPV-DNA probes, for the production of viral capsid proteins using peroxidase-antiperoxidase staining and for whole virus particles using electron microscopy. Fifty-seven per cent (8 of 14) of the wart cultures tested showed persistence of HPV-DNA (5-100 copies HPV-DNA/cell genome equivalent). However, no viral proteins or particles were detected in any culture. This system may prove to be a useful in vitro model for the study of virus-cell interaction and the role of HPV in the malignant conversion of epithelial cells.