The aim of this study is to evaluate different options for introducing liquid-based cytology (LBC) and human papillomavirus (HPV) testing into the UK cervical cancer screening programme. These include options that incorporate HPV testing either as a triage for mild and borderline smear abnormalities or as a primary screening test. Outcomes include the predicted impact on resource use, total cost, life years and cost-effectiveness. Extensive sensitivity analysis has been carried out to explore the importance of the uncertainty associated with disease natural history and the impact of screening. Under baseline assumptions, the cost-effectiveness of different options for introducing LBC appears favourable, and these results are consistent under a range of assumptions for its impact on the diagnostic effectiveness of cytology. However, if we assume a higher marginal cost of LBC in comparison to conventional methods, primary smear testing options are predicted to be more cost-effective without LBC. Combined LBC primary smear and HPV testing with a 5-year interval is similar in both cost and effectiveness to the other 3-yearly options of primary smear testing or primary HPV testing alone. However, both primary HPV testing and combined options would give rise to a far greater risk of inappropriate colposcopy throughout a woman's lifetime. British Journal of Cancer (2004) 91, 84-91. doi:10.1038/sj.bjc.6601884 www.bjcancer.com Published online 25 May 2004