Approximately one quarter of all patients with leg ulcers do not have a "vascular" ulcer, i.e. an ulcer of venous, mixed venous-arterial, or arterial origin. The differential diagnosis encompasses approximately 70 entities, amongst a selection of particular clinical relevance. Martorell hypertensive-ischemic leg ulcer and its two "imitators" pyoderma gangrenosum and necrotizing vasculitides of the skin, necrotic skin infections (e.g., ecthyma, tropical ulcer, and others), chronic wounds caused by physical trauma (contusion (deep dissecting hematoma), radiotherapy or cryotherapy of skin cancers at the leg), leg ulcers in the context of congenital diseases (e. g., Klinefelter syndrome or sickle cell anemia), skin ulcers caused by medical toxicity (hydroxyurea, anagrelide, methotrexate), and last not least ulcerating skin cancer at the legs, primary or secondary in an area of chronic inflammation. Clinical presentations and a pragmatical algorhythm to diagnosis and treatment of these entities are discussed.