The purpose of this study was to examine the determinants of the health behaviour of ethnic groups in relation to alcohol and tobacco use. A cross-sectional questionnaire survey was carried out using network sampling amongst community groups in the South Thames region of the United Kingdom. Self-classified ethnic groups were identified: Black-African; Black-Caribbean; Indian; Pakistani; Bangladeshi and Chinese/Vietnamese. A total of 1113 people were recruited in the study. In all of the ethnic groups, men were more likely than women to smoke tobacco. Chewing of pan and tobacco was common in the South Asian communities and alcohol consumption was high among the Black-Caribbean group. Those factors were predicted by education, employment, gender and being born in the UK. It is important to examine the determinants of such risk behaviours in order to aid appropriate targeting of health promotion interventions, particularly those related to cancer control.