OBJECTIVE: To determine why invasive cervical carcinoma still occurs despite the availability of cervical smear screening services. DESIGN: Questionnaire survey and retrospective study of patient records of women who attended a gynaecological oncology out-patients clinic from 13 February 1997 to 30 June 1997. SETTING: Public hospital, Hong Kong. PATIENTS: Ninety-nine women (median age, 53 years; range, 30-79 years) who gave a history of squamous cervical carcinoma. MAIN OUTCOME MEASURES: The date of the last cervical smear test prior to the development of cervical carcinoma; reasons for non-attendance; attitudes to screening; and the stage and histological diagnosis of disease. RESULTS: Only 19 (19.2%) of the 99 patients had received routine cervical smear testing during the previous 3 years prior to their disease; 76 (76.8%) had not been tested within the past 10 years. The major reasons for not having been tested included being unaware that cervical carcinoma is preventable by screening or can be asymptomatic, being too busy to go for screening, and not knowing where to go for screening. After receiving treatment, 17 (17.2%) of the 99 patients still thought screening was unnecessary and 20 (20.2%) had no idea how frequently smears should be taken. CONCLUSION: The greatest barrier to effective cervical screening is patient ignorance. Public education about cervical smear screening in Hong Kong is needed.