This study compares risk factors for cardiovascular disease in civil servants of three ethnic groups screened as part of the Whitehall II cohort study. Previously identified risk factors for cardiovascular disease in 360 Afro-Caribbean and 577 South Asian subjects are compared with the 8973 white Caucasian subjects. Controlling for socio-economic status is more precise than in most previous studies of cardiovascular differences between ethnic groups. After controlling for socio-economic confounding factors, age and sex, South Asian subjects were found to have increased prevalence of hypertension (defined as either having systolic pressure of > 160, diastolic pressure of > 95 or being on antihypertensives) OR 2.3 (95% CI 1.6-3.3), diabetes OR 4.2 (95%, CI 3.0-5.8) and a high risk lipid profile, although total cholesterol was lower than in the white population. Afro-Caribbean subjects had more hypertension OR 4.0 (95% CI 2.8-5.7) and diabetes OR 2.8 (95% CI 1.7-4.6), but this was accompanied by a favourable lipid profile with low cholesterol and high HDL. Afro-Caribbean alcohol and smoking habits were low-risk. Socio-economic status was found to be an important confounding factor for ethnic differences in biochemical risk factors for cardiovascular disease. However, adjusting for socioeconomic class only attenuates observed differences; it does not abolish them.