OBJECTIVE To assess the performance and impact of primary human papillomavirus (HPV) DNA screening with cytology triage compared with conventional cytology on cervical cancer and severe pre-cancerous lesions.   
 DESIGN Randomised trial.   
 SETTING Population based screening programme for cervical cancer in southern Finland in 2003-5.   
 PARTICIPANTS 58 076 women, aged 30-60, invited to the routine population based screening programme for cervical cancer.   
 INTERVENTIONS Primary HPV DNA test (hybrid capture II) with cytology triage if the result was positive or conventional cytological screening (reference).   
 MAIN OUTCOME MEASURES Rate of cervical cancer, cervical intraepithelial neoplasia (CIN) grade III, and adenocarcinoma in situ (as a composite outcome referred to as CIN III+) during 2003-7 through record linkage between files from the screening registry and the national cancer registry.   
 RESULTS In the HPV and conventional arms there were 95 600 and 95 700 woman years of follow-up and 76 and 53 cases of CIN III+, respectively (of which six and eight were cervical cancers). The relative rate of CIN III+ in the HPV arm versus the conventional arm was 1.44 (95% confidence interval 1.01 to 2.05) among all women invited for screening and 1.77 (1.16 to 2.74) among those who attended. Among women with a normal or negative test result, the relative rate of subsequent CIN III+ was 0.28 (0.04 to 1.17). The rate of cervical cancer between arms was 0.75 (0.25 to 2.16) among women invited for screening and 1.98 (0.52 to 9.38) among those who attended.   
 CONCLUSIONS When incorporated into a well established organised screening programme, primary HPV screening with cytology triage was more sensitive than conventional cytology in detecting CIN III+ lesions. The number of cases of cervical cancer was small, but considering the high probability of progression of CIN III the findings are of importance regarding cancer prevention.   
 TRIAL REGISTRATION Current Controlled Trials ISRCTN23885553.
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