Purpose: Conservative treatment for cervical intraepithelial neoplasia (CIN) by ablative or excisional techniques is widely used. However, women with incomplete excision have a variable risk of CIN recurrence. The aim of this study was to identify possible risk factors for recurrence of CIN after large loop excision of the transformation zone (LLETZ) with involved margins of excision. Methods: All cases of women treated with LLETZ for CIN between 1989-2000, in whom histological evaluation of the excised specimen revealed extension of CIN to the excision margins, were retrospectively studied. A woman was considered to have recurrence when she had histologically confirmed CIN following a second LLETZ or hysterectomy during the follow-up period. The characteristics that were examined as possible risk factors were age, parity, smoking habit, grade of initial lesion and extension to the endo- or ectocervical margin. Results: Treatment failure was diagnosed in 18 out of 65 (27.7%) women with involved margins. The only characteristic that reached statistical significance was age. The mean age of women with recurrence was 35.8 years, whereas the mean age of women without recurrence was 32.8 years (p = 0.044). Also, a trend was evident in women with high-grade initial lesions (CIN II-III) (p = 0.168) and involvement of the endocervical margins (p = 0.149). No differences were observed between the two groups regarding parity and smoking habit. Conclusions: Increased age is a risk factor for recurrence in women with incomplete excision of CIN after LLETZ. Larger studies are required for definite conclusions.