Aim:To evaluate the use of anorectal manometry to select patients for controlled anal dilatation. Methodology: A prospective study was performed using anorectal manometry on all patients with chronic anal fissure who did not have a good response to conservative treatment. Those with increased anal resting pressure were treated with controlled anal dilatation using a two valved anuscope. A second anorectal manometry was indicated after controlled anal dilatation. Results: 19 patients without anorectal pathology (Healthy Control Group) and 57 patients with chronic anal fissure were included in this study. Controlled anal dilatation was performed on 27 patients, maximum resting pressure 122 ± 19 mmHg. In the controlled anal dilatation group the healing rate was 92.5%, mean maximum resting pressure post-controlled anal dilatation was 91 ± 30 mmHg. We found one case of transitory anal incontinence (3.7%). None of the patients had anal incontinence at 18 months of the follow-up. In the remaining 30 patients non selected for controlled anal dilatation (chronic anal fissure control group), a proportion of 53.3% recurrences were registered after conservative treatment. Conclusions: Anal healing of chronic anal fissure and a significant decrease in maximum resting pressure recorded by manometry confirms the success of this procedure. The manometric evaluation of the maximum resting pressure is useful in the selection of chronic anal fissure patients for controlled anal dilatation. The efficacy of dilatation to treat chronic anal fissure in patients with raised anal sphincter pressure was high and complications were rare.