This publication presents the results of postoperative manometric investigations of 77 patients with anal fissure treated within the time span 1985-1997 by lateral sphincterotomy (LS). Results of manometric investigations are compared with digital anal examinations and subjective complaints of patients. Digital anal examination correlated with manometry results in 52 cases (68%). The correspondence between these two results was proved in 48 cases when normal finding was present. An increased sphincter tonus was found in 3 patients, all of them having the anal fissure recurrences. A marked sphincters insufficiency, which had been manifested by stool and gas incontinence was found in one case. When searching for the reason of this complication we found out that this operation procedure had been performed by an unexperienced team of surgeons. In 25 cases (32%) the digital anal assessment and manometric measurement were different. Nevertheless, the clinical symptoms in this group of patients were rather poor. To conclude we may state that manometry provides important data for preoperative evaluation of anal sphincter function and should be performed prior to lateral sphincterotomy operation at least in women.