This research addresses an important methodological issue on patient safety and obesity for the purposes of examining clinical and administrative data for the reliability of using International Classification of Diseases (ICD) diagnoses codes alone to reliably identify obesity as a comorbidity and risk factor in care and management. The findings of this research confirm ICD codes for the obese surgical populations were underutilized. Despite more than 70% of patients classified as overweight or obese, ICD-9 codes for obesity were assigned in less than 10% of the overall sample. Patients in the extreme category of obesity (body mass index [BMI] >40 kg/m2) were more likely to have a corresponding ICD-9 code compared with patients in the BMI range of 25 to 40 kg/m2. International Classification of Diseases, Ninth Revision coding for obesity was underutilized in patients with a BMI of greater than 25 kg/m2. The associated health risks, costs, and potential adverse events associated with obesity make it imperative to continue to study the barriers to coding.