The aim was to determine the burden of diabetes mellitus (DM) in an urban area of China to aid us in planning preventive measures for those at risk of DM. A survey was conducted among the 29,859 subjects aged between 30 and 64 belonging to 32 units of the Shougang Corporation (a heavy industry enterprise) within the Beijing area. WHO study protocols and diagnostic criteria were used to determine the prevalence of DM and impaired glucose tolerance (IGT). The results showed that the age-adjusted prevalence of DM and impaired glucose tolerance (IGT) was 3.63% and 4.19%, respectively, both increasing with age. Peak prevalence for both occurred in the 60-64 age group. Prevalence showed no difference between the sexes in DM but was higher for females in IGT. Obesity, being overweight, a family history of diabetes mellitus and in women, a history of delivering babies with macrosomia, all correlated closely with the prevalence of DM and IGT. High protein intake was also associated with DM, Smoking had no effect on either DM or IGT. Intellectual workers had a higher incidence of IGT than manual workers. Seventy per cent DM was undiagnosed prior to the survey. This survey, done according to the recommendation of WHO, and including appropriate adjustments, reflects the growing prevalence of DM and IGT in this population. It can be compared with other studies for epidemiological analysis.