Because human papillomavirus (HPV) is sexually transmitted, as are pelvic inflammatory disease (PID) agents, the authors investigated whether cervical intra-epithelial neoplasia (CIN) are more frequent in women under treatment for PID. The study involved 298 patients hospitalized for PID, in whom CIN were investigated by smears and colposcopy. CIN were diagnosed in 42 patients, i.e. in 14% of patients: 21 low-grade CIN and 21 high-grade CIN, including one case of early-stage microinvasion. These figures are to be compared to the 0.5-4% of pre-cancerous lesions found in the general population. Screening smears are frequently inaccurate and direct colposcopy appeared preferable. No clinical study of this type has been published before, but certain authors have mentioned a high CIN incidence in patients with PID histories or followed up in sexually transmitted disease centers. These results show that CIN are more frequent in patients treated for PID; CIN should be investigated systematically in this population.