Anal fissure is a most common painful condition whichcauses considerable morbidity and affects the patients quality of life to a greater extent. The majority of acute anal fissures heal spontaneously. However, some of the acute anal fissures do not resolve but become chronic. Thiswarrantsprompttreatmentof the condition with appropriatemethods.Selecting a better method of treating this condition that can achieve optimal clinical results and getting the least pain and inconvenience to the patient has always posed a challenge to the surgeons. This has led to the innovation of a number of surgical and pharmacological methods that relaxes the anal sphincter. Aimof The Study:To study the different clinical presentations and etiological factors of the fissure in ano& different modalities of treatment of fissure in ano i.e., application of 2% Diltiazem ointment, Lords Anal Dilatation and Subcutaneous Lateral Internal Sphincterotomy. &to evaluate the efficacy Subcutaneous Lateral Internal Sphincterotomyas a treatment modality in the management of chronic anal fissure in comparison with application of 2% Diltiazem ointment & with Lords Anal Dilatation. Materials & Methods: The material for the study was taken from the cases attending thesurgery OPD and admitted In-patients of all the units of the Department of General Surgery, Navodaya Medical College Hospital & Research Centre,whowerediagnosed to haveChronicanal fissure. This study was a prospective study which included 90 patients presenting with chronic anal fissure over a period of 18 months from November 2019 to May 2021.Thesepatientswererandomly selectedandclassifiedintothree groups(A,B,C) eachconsistingof30 patients & each group with one type of treatment modality, like group A for 2% diltiazem, B for lords anal dilatation & C for LIS. Follow-up of the patients was done by history and per-rectalexamination to assess the efficacy of the treatment and the complications like pain,bleeding,sphincter spasm, dischargeperanum and incontinence. Results :This study showed the results in favour of Lateral Internal Sphincterotomywith a healing rate of 100% with faster pain-relief and minimal or no complications ifperformedbythehands of an experienced surgeon, whereas latency in the clearance of symptoms and lesions was seen with 2% Diltiazem and Lords Anal Dilatation with adverse effects as well. With the healingrate of 100% of Fissure-in-ano in LIS therapy group, 81% in Lords Anal Dilatation and 71% with topical 2% Diltiazem therapy, & adverse effects or complications being maximum in 2% Diltiazem therapy group, 13 patients (46%) when compared to Lords Anal Dilatation (41% , 11 patients) and LIS group (32%, 09 patients), weconcludethatLateralinternalsphinterotomy(LIS) appearstobethebetterlineoftreatmentasthereis 100%healingrate, minimal complications and no recurrence.