This issue of The Journal of the American Dental Association (JADA) contains a report1 of the periodontal treatment response among people who participated in the Diabetes and Periodontal Therapy Trial (DPTT).2 The DPTT is a large, multicenter randomized controlled clinical trial that was designed to study the effect of nonsurgical periodontal therapy among people who have type 2 diabetes mellitus and periodontitis. The periodontal treatment consisted of two or more sessions of scaling and root planing (totaling more than 2.5 hours and involving the use of local anesthetic) and follow-up supportive periodontal care. The main conclusion of this six-month trial was that nonsurgical periodontal therapy did not improve glycemic control in patients with type 2 diabetes who had periodontitis.2 This trial has received considerable attention because its findings are contrary to what many people anticipated—and because it did not support results of smaller clinical trials and meta-analyses that showed improvements in hemoglobin A1c (HbA1c) levels as a result of nonsurgical periodontal therapy.3 We wish to address the generalizability of the DPTT. As reported by the authors in this issue of JADA,1 the patient sample of the DPTT reflects the population of people with diabetes in the United States. The DPTT included participants who had type 2 diabetes with HbA1c levels between 7 percent and less than 9 percent; 72 percent of the participants were obese (body mass index [BMI] greater than 30 kilograms per square meter).1 The National Health and Nutrition Examination Survey is a population-based survey of people with diabetes in the United States; its results demonstrated that only 12.6 percent of people with diabetes in the United States are estimated to have HbA1c levels greater than 9 percent and 62.4 percent to have a BMI of 30 or greater.4,5 The DPTT does not address the possible effect of periodontal treatment in the 12 percent of the population with HbA1c levels greater than 9 percent or the 50 percent of the population with HbA1c levels less than 7 percent, because efforts were made to exclude these patients. However, the magnitude of obesity was not constrained by trial entry criteria. Patients with type 2 diabetes who have HbA1c levels higher than 9 percent and a BMI of less than 30 are rare. Because the participant sample was typical of patients with diabetes both in terms of HbA1c and obesity, the results of the DPTT should be viewed as fully generalizable to patients with diabetes in the United States.