Objective: This study considers the physical activity (PA) and dietary habits of British young people according to socio-economic status (SES). Methods: The PA and dietary habits of 98 boys and 101 girls (12.9 0.3 years) from two Welsh secondary schools (school 1 and school 2) were examined. Free school meal eligibility and Census 2001 data were used as indicators of SES. School 1 was designated high SES, while school 2 represented low SES. Participants were classified according to SES. Physical activity was estimated by seven-day recall and questionnaire; dietary patterns were assessed using a seven-day food diary and questionnaire. Results: Two-thirds of all participants had not taken part in vigorous activity over the last week. Furthermore, 83.8 per cent of participants did not meet the Health Education Authority's recommendation of one hour per day moderate activity. Boys were more active than girls, (P less than or equal 0.05), but SES did not influence time spent in activity. Ninety-four percent of participants were taken to school via motorized transport. There were no significant differences in fat intake between the sexes or across SES. In addition, 93 per cent of the participants, irrespective of SES, exceeded the 10 per cent saturated fat cut off point recommended by the World Health Organization. Conclusion: Physical activity and dietary patterns are modifiable through suitable lifestyle changes. The present data support the notion that preventative strategies for combating chronic diseases should begin early in life and across socio-economic statuses. (Contains 4 tables.)