The dental profession is acutely aware of oral health problems associated with diabetes mellitus and clinical manifestations indicative of occult forms of the disease. Periodontal disease is common in patients with diabetes, and its effective management in diabetic patients requires cooperation involving the patient, physician, diabetes educator, dentist, and other allied health care providers. While these patients categorically appear more prone to diseases affecting the supporting tissues of the teeth, preservation of functional dental integrity can be attained by effective control of contributing systemic and local factors. This paper will discuss periodontal disease, its relationship to diabetes, proposed mechanisms of interaction, and management of periodontal disease in the diabetic patient.