The increasing incidence of sexually transmitted infection (STI) in young people is one of the most important social and health problems in Japan,¹ and recent changes in the sexual behaviour may be an important factor.² Cervical human papillomavirus (HPV) infection is one STI and is the major cause of cervical cancer, which is the cancer with the second highest incidence rate and fifth highest cause of cancer death in women worldwide.³ Japan is an area with the second lowest incidence of cervical cancer worldwide.³

To investigate the prevalence of STIs, we performed a cross sectional study of women attending gynaecology departments in the Hokuriku area of Japan from July 2000 to July 2003. In all, 797 women between 15 and 62 years old were selected from about 15 000 women who had visited and had a cervical cytology test in one of five clinics during this period. After obtaining written informed consent, all the subjects were given to pelvic examinations, a cervical cytology test, and an STI test using the cervical scraped cell samples. DNA for high risk HPV (HPV types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, and 68), Chlamydiatrachomatis, and Neisseriagonorrhoeae was detected using hybrid capture assays (Digene, USA) performed at the Mitsubishi Kagaku Clinical Laboratory in Tokyo (Japan). To document each subject’s occupation and sexual behaviour, they were given a questionnaire that they completed independently and returned in a sealed envelope. The questionnaires and clinical data were sent directly to the research centre at …