AIM: To determine the frequency of cervical intraepithelial neoplasia (CIN) following large loop excision of the transformation zone of the cervix (LLETZ) according to grade and completeness of excision of CIN. METHODS: A retrospective study of 669 patients who had LLETZ biopsies showing CIN 1, 2, or 3. The patients were subdivided according to the grade and completeness of excision of CIN. The follow up period was 1.5 to 3.5 years. Risk of persistent/recurrent CIN was assessed by the frequency of histological diagnosis of CIN during the follow up period. RESULTS: Frequency of persistent/recurrent CIN increased with the grade of CIN reported: 6.7% of patients with CIN 1, 13.4% with CIN 2, and 21.7% with CIN 3 developed persistence or recurrence. The frequency of CIN persistence/recurrence was significantly lower where LLETZ showed complete excision of CIN (8.4%) than where it was incomplete (31.3%) (p < 0.0001) or equivocal (27.8%) (p < 0.0001). CONCLUSIONS: Patients with incomplete or equivocal excision of all grades of CIN merit careful, preferably colposcopic, follow up. Patients with completely excised high grade CIN require careful cervical cytologic surveillance.