The effects of diltiazem treatment on symptoms of chronic anal fissures and their long-term outcome were investigated. One hundred and twelve patients were supplied with 6-week course of 2% diltiazem cream for twice-daily topical application. The medical notes and extended follow-up by telephone for 112 patients were recorded and statistically analysed. The success rate and satisfaction of topical diltiazem were each over two thirds. Nearly 80% of patients reported no adverse effects, and it seems that those complaints attributed to diltiazem rarely led to reduced compliance. After diltiazem therapy for fissure, 59% of patients required further treatment (medical and/or surgical) over the average 2-year period of follow-up. The reported adverse effects of topical diltiazem treatment in patients with anal fissures were more common than previously thought, although compliance was rarely affected. During consultation regarding the advantages and disadvantages of surgical vs. chemical sphincterotomy, patients should be aware that the majority of patients receiving diltiazem as the primary treatment for anal fissure subsequently require further treatment.