Studies on the theme of optimal cutoff values of waist circumference (WC) and waist-to-hip ratio (WHR) for assessing risk of type II diabetes were reviewed. Twenty-eight studies of individuals aged 18-74 years are eligible for inclusion. Four of these studies are prospective and the rest are all cross-sectional. Tongans had the highest WC (103 cm for both men and women) cutoff value (but not for WHR), followed by studies in the USA and U.K. The WC cutoff values were higher for all races in the USA and the UK studies compared with their counterparts in their original countries. The optimal WC (WHR) cutoff values were 97-99 cm (0.95) for White men and 85 cm (0.83-0.85) for White women living outside the USA and the UK, whereas they were 85 cm (0.90) for Asian men and 75-80 cm (0.79-0.85) for Asian women; the values for other ethnic groups were between those for White and Asians. Men had higher values than women in White, Chinese, Japanese, Indians and Bangladeshis, but not in Thai, Iranians, Iraqi, Tunisians, Mexicans, Africans and Tongans. At these optimal cutoff points the sensitivities were around 60-70%, which was higher or equal to the specificity. There is no universal cutoff value that can be applied worldwide, and a country-specific value should be considered taking into account the purposes and resources.