Aim To assess the value of using smooth muscle relaxants drugs and assess the results of the topical use of 2% diltiazem as an alternative to 0.2% nitroglycerin in the treatment of chronic anal fissure (CAF). Methods Review of the CAF contained in a prospectively collected database of anal fissures including one hundred forty-five patients diagnosed with CAF and treated with standard measures (ST) in two consecutive periods. During the first period they were allocated alternatively to not receive further treatment (ST group) or to be treated with nitroglycerin ointment (NTG group). In the second period all were treated with local diltiazem (DTZ group). One hundred forty-five patients entered the study and 124 completed it. Results Initially there were significant differences in improvement rates (45% ST, 62.5% NTG and 80% DTZ, p<0.01), but not in the cure rates (27% ST, 40% NTG and 39% DTZ) and the treatment was completed by 124 patients (85.5%). There were more side effects and more dropouts in the NTG group. In the subsequent follow-up for a median period of 25 months there were 25% recurrences and almost all responded to repeated medical treatment. Conclusions Smooth muscle relaxant drugs do not achieve a higher cure rate than the traditional measures used in CAF, but offer more symptomatic relief, providing an opportunity to avoid surgery. Topical diltiazem does not have the side effects of the nitroglycerin and is better accepted by patients.