In Germany about 0.7% of the adult population have a chronic leg ulcer. Although chronic venous insufficiency accounts for at least 80% of all chronic leg ulcers, knowledge of the relevant differential diagnostic considerations is of crucial importance, in particular for patients who are refractory to therapy. In addition to vascular disease, other causes include neuropathic, metabolic, hematologic and exogenous factors as well as neoplasias, infections, drugs, genetic defects and some primary skin disorders. For the long-term successful treatment of patients with chronic leg ulcers, it is necessary to identify all relevant factors, in order to enable a pathogenesis-oriented, interdisciplinary therapeutic approach.