OBJECTIVES: To determine payments made by commercial health care providers for adults diagnosed with obesity, and those who are comorbid with any combination of the following chronic conditions: diabetes mellitus (DM), hypertension, depression, and/or congestive heart failure (CHF). METHODS: We utilized a 10% random sampling from a commercial claims and encounters database (n=12,416,190). The study population (n=50,717) was limited to those who: 1) were adults age 18-64; 2) filed a claim between 2006-2007; 3) had at least one inpatient visit, one outpatient visit, or one emergency department visit; and; 4) had been given a primary or secondary diagnosis of obesity. Persons were identified and categorized if they had one or more comorbid diagnoses (DM, hypertension, depression, and/or CHF) in addition to obesity. After adjusting for age and gender, we calculated the mean total net expenditures (in $US 2007) for each combination of comorbid conditions. All calculations were performed in Stata. RESULTS: Among those diagnosed with obesity, the mean net expenditures for services were $1799 per patient. Persons diagnosed with obesity and other comorbidities observed an increase in total net expenditures. Obesity and hypertension observed the highest increase among single comorbidities at $4298. For persons with obesity and two other comorbidities, DM and depression was the highest at $14,364.  The most expensive condition in the study sample was obesity, DM, hypertension and depression at $14,843. All results were statistically significant at the 95% confidence level. CONCLUSIONS: Compared to the average medical claim, persons diagnosed with obesity along with other common chronic conditions experience significant increases in healthcare costs. These costs are often driven higher by the time spent as inpatients. In many cases, obesity may be the cause of other chronic conditions that result in these high costs. Thus, by controlling and reducing the prevalence of obesity, we may see significant decreases in health care expenditures.