This thesis reports three studies which examined the development of cultural practices, social identifications and inter-group attitudes in 7- to 11-year-old British children living in London. In studies 1 and 2, 32 ethnic minority and 12 English ethnic majority children participated in qualitative one-to-one semi-structured interviews. Results revealed that the minority and majority group children had multiple identifications which were context-dependent; had adopted multi-cultural practices which were often domain and context specific; and that there was variability in the relationship between the children's social identifications and cultural practices. In study 3, 244 English, Indian and Pakistani children participated in a quantitative study designed to examine the development of inter-group attitudes and prejudice, and to explore whether children's inter-group attitudes are related to their levels of ethnic, national and religious identification, their patterns of inter-group friendships, their levels of appropriation of cultural practices drawn from ethnic cultures other than their own, and their cognitive classification ability. Results showed that there was variability in the children's social identifications and intergroup attitudes as a function of their ethnicity; that there were no age-related differences in the children's inter-group attitudes, inter-group friendships, identifications and cognitive classification skills; that there was no evidence of negative prejudice towards ethnic out groups; and that inter-group attitudes, identifications, cultural practices, and classification skills were largely independent of each other. There were differences in the children's cultural practices as a function of ethnicity, gender and age, and they appeared to have adopted a multi-cultural integration acculturation strategy with their cultural practices varying according to cultural domain and context. It is argued that the existing dominant theories of ethnic attitude development in children, acculturation and contact cannot explain the patterns of development found in the present data, and that there is a need for new theories in this field.