OBJECTIVES: To examine the prevalence of risk factors for diabetes and its complications in the Co-operation Council of the Arab States of the Gulf (GCC) region. DESIGN: Systematic review. SETTING: Co-operation Council of the Arab States of the Gulf (GCC) states (United Arab Emirates, Bahrain, Saudi Arabia, Oman, Qatar, Kuwait). PARTICIPANTS: Residents of the GCC states participating in studies on the prevalence of overweight and obesity, hyperglycaemia, hypertension and dyslipidaemia. MAIN OUTCOME MEASURES: Prevalences of overweight, obesity and hyperglycaemia, hypertension and hyperlipidaemia. RESULTS: Forty-five studies were included in the review. Reported prevalences of overweight and obesity in adults were 25-50% and 13-50%, respectively. Prevalence appeared higher in women and to hold a non-linear association with age. Current prevalence of impaired glucose tolerance was estimated to be 10-20%. Prevalence appears to have been increasing in recent years. Estimated prevalences of hypertension and dyslipidaemia were few and used varied definitions of abnormality, making review difficult, but these also appeared to be high and increasing, CONCLUSIONS: There are high prevalences of risk factors for diabetes and diabetic complications in the GCC region, indicative that their current management is suboptimal. Enhanced management will be critical if escalation of diabetes-related problems is to be averted as industrialization, urbanization and changing population demographics continue.