OBJECTIVE: This study was performed to evaluate the diagnostic accuracy of colposcopy-guided biopsy during electric conization and to analyze predictive factors for residual tumor after electric conization in patients with microinvasive cancer of cervix. METHODS: We reviewed 104 patients with electric conization performed at the Department of Obstetrics and Gynecology, Chungnam National University Hospital from January 1992 to December 2000. We investigated the significance of the margin state according to using colposcopy or not , age, number of specimen, and lesion size. RESULT: The results of each method were analyzed with histopathologic findings of the surgical specimen. The resection margin was involved in 13% of patients who received electric conization under colposcopy-guide. This proportion was significantly lower than in patients without colposcopy-guide (48%). The resection margin was involved in 46% of patients aged over 45 years. This proportion was significantly higher than in patients less than 45 years (26%). But number of specimen and lesion size did not influence the resection margin status. CONCLUSION: These results suggest that colposcopy-guided biopsy seems to be essential during the diagnostic conization of microinvasive cancer of cervix.