Geographic or ethnic differences in the occurrence of disease often provide insights into causes of disease and possible opportunities for disease prevention. Persons in China appear to have a consistently lower prevalence of rheumatoid arthritis and fibromyalgia than persons in the United States and Europe; reasons for these prevalence differences might include genetic differences, differences in environmental exposures or a combination of both. With increasing obesity, gout is becoming endemic in China. Finally, symptomatic knee osteoarthritis is extremely common in China and constitutes a major public health problem there.