To determine the prevalence of diabetes and impaired fasting glycaemia (IFG) and associated conditions such as obesity and hypertension, in the multi-ethnic, adult population of the United Arab Emirates in 1999-2000. A stratified, multistage, random sample was selected. Diagnosis was based on the latest recommendations of a WHO Expert Group. The overall response rate was 89%. Crude prevalence of diabetes was 20%. It was higher in UAE citizens (25%) than in expatriates (13-19% depending on country of origin). Prevalence of diabetes rose with age to a maximum of 40% after the age of 55 years. Prevalence of impaired fasting glycaemia was 5% in men and 7% in women. Forty-one percent of subjects with diabetes were undiagnosed prior to the survey. Of the previously diagnosed subjects with diabetes, 59% were taking oral hypoglycaemic agents, 8% used insulin and 17% relied on diet alone. Obesity was common in all ethnic groups. Approximately three-quarters of all subjects were either obese (BMI> or =30) or overweight (BMI 25-29). Presence of diabetes was associated with increasing waist-hip ratio (WHR), age and with systolic blood pressure and ethnicity. Co-morbidity with glucose intolerance occurred with obesity in 8% and with hypertension in 5%. Three-quarters of all subjects had one or more of these conditions. Diabetes, obesity and hypertension are extremely prevalent in the adult population of the UAE. Prompt action is required to avert a major public health crisis due to the long-term complications of diabetes in the near future.