The original material of monitoring of 118 patients with chronic anal fissure is presented in the article. Patients' mean age was 48.9+-10.5 years. It was used injections of medicine of botulinum toxin of type A (Lantox) by its introduction in internal anal sphincter in all patients. There was granulating wound with signs of marginal epithelialization in 59.3% of cases on the 10th day after injection. It was detected complete epithelialization of dermis defect in 93.2% of cases on the 21st day, after six weeks - in 100% of cases. According to anorectal profilometry the index of maximal and average pressure in the anal canal at the level of the internal sphincter in patients at rest decreased to norm. Lantox introduction leads to rapid and persistent reduction of pain intensity. "Lantox" use in ambulatory practice permits to minimize the indications for surgical treatment.