Objectives Evaluation of the results of treatment of adenocarcinoma in situ by loop electrosurgical excision procedure and the safety of a conservative strategy. Methods Identification of all cases of adenocarcinoma in situ treated by loop electrosurgical excision procedure at our institution and follow-up by a conservative strategy. Completeness of the identification of all cases was secured by data from the National Pathology Registry. The treatment strategy was based on cytologic follow-up performed by a general practitioner and, irrespective of margin status of the cone, only the results of the postoperative surveillance were indicative of further treatment. Results A total of 224 patients were identified. The overall recurrence rate with a mean follow-up time of 87.8 months was 7.6% (17/224). The recurrence rate in patients with involved margins was significantly higher than in patients with uninvolved margins, 15.7% vs 5.2%, respectively. Six recurrences were diagnosed at first examination 6 months postconization in patients with involved margins. They were treated with hysterectomy in 4 cases and reconization in 1 case. If involvement of margins alone had been an indication of further therapy (hysterectomy or reconization) immediately after conization, the conservative management strategy prevented 46 surgical procedures. Two cases of invasive cancer were diagnosed during follow-up, 150 months and 196 months after primary treatment, and after normal follow-up examinations. These 2 cases must be considered de novo cases and cannot be considered treatment failures. Conclusion The conservative management strategy thus seems safe, and unnecessary surgical procedures were avoided.