Aims/hypothesis: The Anglo-Danish-Dutch study of intensive treatment in people with screen-detected diabetes in primary care (ADDITION) is a pragmatic randomised controlled trial of the effectiveness of intensified multi-factorial treatment on 5 year cardiovascular morbidity and mortality rates in people with screen-detected type 2 diabetes in the Netherlands, UK and Denmark. This paper describes the baseline characteristics of the study population, their estimated risk of coronary heart disease and the extent to which that risk is potentially modifiable. Methods: Stepwise screening strategies were performed using risk questionnaires and routine general practice data plus random blood glucose, HbA1c and fasting blood glucose measurement. Diabetes was diagnosed using the 1999 World Health Organization criteria and estimated 10 year coronary heart disease risk was calculated using the UK Prospective Diabetes Study risk engine. Results: Between April 2001 and December 2006, 3,057 people with screen-detected diabetes were recruited to the study (mean age 59.7 years, 58% men) after a stepwise screening programme involving 76,308 people screened in 334 general practices in three countries. Their median estimated 10 year risk of coronary heart disease was 11% in women (interquartile range 7-16%) and 21% (15-30%) in men. There were differences in the distribution of risk factors by country, linked to differences in approaches to screening and the extent to which risk factors had already been detected and treated. The mean HbA 1c at recruitment was 7.0% (SD 1.6%). Of the people recruited, 73% had a blood pressure ≥140/90 and of these 58% were not on antihypertensive medication. Cholesterol levels were above 5.0 mmol/l in 70% of participants, 91% of whom were not being treated with lipid-lowering drugs. Conclusions/ interpretation: People with type 2 diabetes detected by screening and included in the ADDITION study have a raised and potentially modifiable risk of CHD. ClinicalTrials.gov ID no.: NCT 00237549.