The heights and weights of 1,749 Special Olympics athlete volunteers participating in the Special Olympics Games in 1999 and 2001 were measured, and body mass index (BMI) was computed. Results indicated that athletes from the United States (US) under 18 years of age had a significantly (P<.001) higher prevalence of being overweight or at risk of being overweight compared with athletes from other countries. Similarly, adult athletes from the United States were at least 3.1 times more likely to be overweight or obese compared with their non-US counterparts. The risk of obesity in US Special Olympic athletes parallels the prevalence of obesity in the general US population. There is a clear need for further research, surveillance, and treatment of the risky health behaviors that contribute to the development of obesity in this group.