&NA;Changes in anal sphincteric manometric pressures in response to rectal distention were measured in eight patients with chronic anal fissures and were compared with the of ten controls. No statistically different resting pressures were noted between the two groups. Overshoot phenomenon was more commonly seen in patients with fissure. There were no differences in the anal sphincteric pressures after lateral internal sphincterotomy (LIS) or fissurectomy midline sphincterotomy (FMS). All fissures healed postoperatively, irrespective of the surgical technique (LIS or FMS) or the pressure readings. It can be concluded that the therapeutic effect of sphincterotomies might at least in part be due to anatomic widening of the anal canal rather than to decreased resting pressures of the internal sphincter.