Objective. To investigate the prevalence and incidence of non-insulin dependent diabetes (NIDDM) in China by WHO criteria. Methods. In the prevalence survey of NIDDM all 110 660 participants (55 391 men, 53 269 women) a ere inhabitants of Daqing City, the largest oil center in northeast China, accounting for 87.3% of the 25 to 74 aged population in this city. They were screened by measuring two-hour plasma glucose concentrations (PG2h) after a breakfast containing at least 80 g of carbohydrate, then a standard oral glucose tolerence test (OGTT, 75 g glucose load) was performed in 4209 subjects with PG2h more than 6.67 mmol/L in this screen. NIDDM and impaired glucose tolerence (IGT) were diagnosed using WHO criteria. Incidence survey was made in 36 471 non-diabetics identified in the prevalence survey. Two-hour urine-glucose after breakfast was determined during first screen. The urine-glucose trace or positive subjects were then followed by OGTT. Glucose was measured by glucose oxidation method. Results and Conclusions, In prevalence survey, 630 newly diagnosed NIDDM (296 males, 334 females) and 596 IGT (318 males, 278 females) were found in 110660 (male:female= 55 391/ 53 269) studied subjects in addition to 190 previously diagnosed NIDDM. Thus the total prevalence of NIDDM was 7.7/ 1000, and IGT was 5.5/1000. Standardized to the Chinese population in 1982, the prevalences are 12.6 / 1000 (95% CI=12.0 / 1000-13.3 / 1000) and 7.7 / 1000 (95% CI=7.16 / 1000-8.19 / 1000) respectively. In the survey, 191 NIDDM (103 males, 88 females) were diagnosed in the 36 471 (male:female=18 801/17 670) non-diabetics from 1986 to 1990, thus the annual incidence of NIDDM was 131/100 000 (137 males, 125 females). Standardized incidence is 131/100 000 (95% CI=94/100000-168/ 100 000). It is estimated that there would be more than 700 thousand new diabetics per year in 24-74 years old Chinese if Chinese population were 1.3 billion in the early 21st century.