Diabetes affects almost 30 million Americans, of which 0.3 %, or almost 90,000 will sustain Charcot arthropathy yearly, and many more will experience ulceration. Both of these conditions are major precursors to one of the most dreaded complications of diabetes—amputation. This chapter examines the classification of these two separate but related conditions. Classification systems of Charcot arthropathy may be divided into two general categories, anatomic and temporal. Anatomic classification systems describe the location of the disease about the foot and ankle, while temporal staging systems describe the varied characteristics of this disease over time. Anatomic classification systems are important, as Charcot arthropathy behaves uniquely based on the location of disease about the foot and ankle. Appropriate treatment also depends on the stage of disease, which requires an accurate temporal staging system. Several classification systems are described, with each providing unique insights into this complex disease. In addition, four classification systems of diabetic foot ulcers will be reviewed as well.