Background Invasive cancer of the cervix is considered a preventable disease because it has a long pre-invasive state,cervical cytology screening programs are currently available,and treatment of pre-invasive lesions is effective.We tested the accuracy of frozen section examination (FSE) of cone specimens to identify the endocervical margin and rule out invasion in patients with high-grade cervical intraepithelial neoplasia (CIN).Methods For 320 consecutive patients with a preoperative biopsy result of CIN stage 2/3,cold-knife conization (CKC)was performed followed by FSE.The results from analyses of permanent paraffin sections (PS) were compared with the FSE findings.Results The accuracy of FSE was 87％ (278/320).For all of the seven patients with an invasive squamous cell carcinoma of the cervix identified by FSE,the diagnosis was confirmed by PS analysis.For one patient,the FSE result was cervicitis,whereas PS ananlysis showed microinvasive carcinoma.Appropriate surgery was performed for all patients based on the FSE and biopsy results.The FSE and PS results were not significantly different (P=0.000).Definitive examination of margin status using PS was concordant with FSE findings in all cases.Conclusions FSE is a rapid and reliable method for evaluating CKC specimens.It can identify frank invasion,permit adequate treatment in a one-stage procedure,and reliably detect clear resection margins.Since discrepancies do exist and may result in inappropriate treatment,further research is required to decrease these discrepancies and avoid missing even one case.