AIM--To assess the value of detecting human papillomavirus (HPV) DNA in false negative archival cervical smears in population based screening programmes for cervical cancer. METHODS--Cytomorphologically classified false negative archival Pap smears (n = 27) taken from 18 women up to six years before cervical cancer was diagnosed were blindly mixed with 89 smears from hospital patients with a variety of gynaecological complaints and tested for HPV by the polymerase chain reaction (PCR). Corresponding cervical cancer biopsy specimens were also available for HPV analysis. Neither the examining cytopathologist nor the molecular biologist was aware of the study design. RESULTS--HPV DNA was detected in the smears of 16 patients with cervical cancer missed previously by cytology. HPV 16 and 18 were found predominantly in those smears taken up to six years before the diagnosis of cervical cancer. The smears of the two remaining patients were reclassified as inadequate for cytology or contained no suitable DNA for PCR. In 15 patients the same HPV type could be found in the smears and the cervical cancer biopsy specimens. CONCLUSIONS--The results indicate that high risk HPV types can be detected in archival smears classified as false negative on cytology and that cytological screening errors may be reduced if combined with PCR testing for HPV.