This study determined the prevalence of coronary heart disease (CHD) risk factors in young people of differing socio-economic status (SES). A cohort of 100 boys and 108 girls, aged 12.9, SD 0.3 years drawn of differing SES were assessed for CHD risk factors. Measurements included indices of obesity, blood pressure, aerobic fitness, diet, blood lipids and lipoproteins. Significant differences (P [less than or equal to] 0.05) were detected with respect to SES, for systolic blood pressure, total cholesterol and low density lipoprotein cholesterol, but in boys only. Significant sex differences (P [less than or equal to] 0.05) were identified for systolic blood pressure, diastolic blood pressure, aerobic fitness, waist to hip ratio, summation of four skinfold thicknesses, average daily kilocalorie intake, total cholesterol and low density lipoprotein cholesterol. Moreover, increased body fatness, low aerobic fitness, a high fat diet and elevated lipoprotein (a), were the most frequently identified CHD risk factors in this cohort. This study reveals a high incidence of CHD risk factors in young people irrespective of SES and sex, and highlights the need for vigilance in identifying such risk factors from a young age. (Contains 4 tables and 1 note.)