This article reviews and describes trends and differences in prevalence of type 2 diabetes mellitus of Chinese populations in Mainland China, Hong Kong and Taiwan based on literatures published in the MEDLINE Advanced database (January 1966-October 2005) in both Chinese and English languages. Chinese populations in Hong Kong and Taiwan have significant higher prevalence rates of diabetes than their Mainland counterparts, with odds ratios 1.5 (95% confidence intervals: 1.4, 1.7) and 2.0 (95% confidence intervals: 1.8, 2.2), respectively in 1995-2003 adjusted for age and diagnostic criteria. Using stratified diagnostic criteria; the odds ratios in Hong Kong and Taiwan were consistently higher than Mainland China for the periods of 1985-1994 and 1995-2003. A large proportion, i.e. 68.6% (95% confidence intervals: 67.4%, 69.7%) of diabetic patients remains undiagnosed in Mainland China as compared to 52.6% (95% confidence intervals: 49.8%, 55.5%) undiagnosed in Hong Kong and Taiwan. The prevalence rates of diabetes and impaired glucose tolerance of the Chinese populations rise in older age groups. In tandem with economic development and change toward lifestyle that is lack of physical activity and rich in high-fat diet, prevalence of diabetes of the Chinese populations are on the rise. If the undiagnosed individuals left uncontrolled, they are subject to higher risks of developing diabetes and its complications. These will increase the burdens of diabetes medically and financially.