Anal fissures are a common cause of anal pain during, and for 1 to 2 hours after, defecation. The cause is not fully understood, but low intake of dietary fibre may be a risk factor.We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of non-surgical treatments for chronic anal fissure? What are the effects of surgical treatments for chronic anal fissure? We searched: Medline, Embase, The Cochrane Library, and other important databases up to August 2009 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).We found 28 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.In this systematic review we present information relating to the effectiveness and safety of the following interventions: anal advancement flap, anal stretch/dilation, botulinum A toxin-haemagglutinin complex alone or with nitrates, calcium channel blockers, internal anal sphincterotomy, and nitric oxide donors.