The anal fissure syndrome is characterized by a triad: anal pain accompanying defaecation; one or several anal ulcers; anal internal sphincter hypertonia. Fissure in ano is the most frequent cause; diagnosis is clinical; pathogenic understanding and treatment are in rapid progress. Secondary anal fissurations are characterized by a less typical syndrome, by the necessity of special investigations for diagnosis and by an etiology-oriented treatment. Their causes are multiple. The most frequent are infectious, essentially sexually transmitted diseases, and the tumour, mainly anal epidermoid cancer.