Background:Chronic anal fissures are harder to treat and surgery may be the best option. The goal of surgery is to help the anal sphincter muscles relax which reduces pain and spasms, allowing the fissure to heal. The aim of the present study was to assess the Improving outcome of patients of chronic anal fissure. Patients and methods: This clinical trial study was conducted in General Surgery Department, Faculty of Medicine, Zagazig University on 18 chronic anal fissure cases. All patients were subjected to full history taking, proper local examination and baseline investigations. Anorectal manometry was performed for all patients preoperatively. Then, bilateral segmental internal sphincterotomy was done for all patients. Results: In our study, age was 37.77 ± 6.44 with minimum of 24 and maximum of 50 years. Regard sex distribution, males and females were matched (50/50 percentage). Majority were posterior (66.7%) then anterior (22.2%) and finally both (11.1%). Operation time was 17.77 ± 3.62 with minimum of 12 and maximum of 25 minutes. After internal sphincterotomy, complete healing was 5.16±1.09 with minimum of 4 and maximum of 7 weeks. VAS significantly decreased from pre to 1st 24 hours till the end of follow up. Incontinence score significantly decreased from preoperatively to 1st week till the end of follow up. Conclusion: bilateral segmental internal sphincterotomy is a novel, safe, and effective way of treating chronic anal fissure, and it is not associated with any risk of anal incontinence.