Foot ulcers are one of the major complications of diabetes. They have a poor tendency to heal, which may result in long-term in-hospital treatment and/or amputation. The foot in diabetic patients is the crossroads of several pathological processes, in which almost all components of the lower extremity are involved: skin, subcutaneous tissue, muscles, bones, joints, blood vessels, and nerves. An understanding of these processes is necessary for the development and application of preventative and management strategies. In this article the pathogenesis of the major abnormalities in the diabetic foot are described, the pathways to ulceration are summarized, and a systematic evaluation of a diabetic patient with a foot ulcer is given.