Trilingualism is a relatively new research field, which has often been studied within the framework established for bilingualism. Although there are overlaps, researchers have consistently pointed out that the dynamics in trilingualism pose greater variations than in bilingualism with an effect on language maintenance. However, the precise nature of this process is still unclear. The aim of this thesis is to examine and describe trilingual families' language practices, with a view to adding to the understanding of the sociocultural and linguistic factors that influence parents whether or not to use their native languages with their children. This study, based on a multi-step survey, was conducted in three phases. First an exploratory pilot study was carried out by interviewing five parents of trilingual families, which helped to develop the interview schedule. The second phase focused on semistructured interviews of parents in 35 trilingual families living in England, before moving to Germany to conduct the third phase by interviewing the parents of a further 35 families. The participants were encouraged to comment on their own language and cultural practices with their children at home and in the wider community. It was found that influences on parents' language choices with their children were multifactorial. Trilingual families in which each parent spoke one different native language other than the community language were highly motivated in England (77%) and Germany (82%) to pass on their native languages and the associated cultural values to their children. This was partly related to the effectiveness of the OPOl (One Parent One language) and the support from grandparents. In contrast, parents who spoke two or more native languages tended to use only one of them with their children partly because the OPOl was impractical or the beginning of school made it harder to use their additional native languages. Finally, multilingual schools in Germany were usually chosen for English only, even if it was not a native language for the parents. Thus, the research findings underscore the complexity of the relationship between linguistic and sociocultural factors that influence trilingual families' language practices.