Three hundred eighty-five women treated with conization due to repeated CIN I, CIN II or CIN III of the cervix uteri have been followed up for 5 years. All cones were classified according to diagnosis and status of the resection margins. A significantly greater recurrence rate of 16.2% was found in the group with neoplasia in the resection margins, in contrast to 3.9% in the group with normal resection margins. However, 83.8% (75.4-92.2%) of patients with neoplasia in the resection margins can be expected to be free of recurrence after a 5-year postoperative follow-up period. Whether the non-free resection margins were endocervical, ectocervical or both, did not influence the recurrence rate. While the prevalence of non-free resection margins increased significantly with increasing dysplasia, this could not be found with increasing age. The risk of recurrence could not be correlated with the grade of dysplasia. We conclude that neoplasia in the resection margins of the cone represents an increased risk of recurrence. Therefore, we changed the normal smear check-up with a cotton-swab to smear with cyto-brush, supplemented with colposcopy in the non-free resection margin group, but it remains to be proven that this procedure is safer.