Anal fissure remains one of the most common proctologic problems. A number of reports have advocated the use of partial internal sphincterotomy as a treatment of chronic anal fissure. Our study shows the results of a retrospective analysis of our patients who underwent lateral internal sphincterotomy for the treatment of chronic anal fissure. To determine long time results we examined random sample of 75 operated patients. Apart from taking careful history and patient's assessment of the operation effect, the patients were investigated "per rectum", and even possibly rectoscopically. To asscertain suitability and also security of properly done internal sphincterotomy, we performed anorectal manometric examinations in 53 patients controlled. To conclude our results, we can state that in 9 (12%) patients controlled some subjective complaints or certain pathologic findings connected with anal fissure or sphincterotomy were found. None of the people from the set of ours suffered from any complaints, which can be taken as stool incontinency. In no patients any change in pressure measured by anorectal manometry indicating incontinency was proved.