In real life situations there are many difficulties in raising children bilingually in a monolingual community, especially when using the “one person – one language” approach; nonetheless modern theory on language acquisition often suggests that bilingual education should be ʽchild´s playʼ. This article is a short presentation of my Ph.D. thesis, which analyses the process of language shift in ten bilingual Italo-German families in Rome. Against the background of current theories about bilingual language education, the actual language situation in these families was reviewed twice in five years, thereby documenting the contradictions between theory and practice. Several factors influencing the process of linguistic adaptation to the dominant language and the more or less successful bilingual education have been identified and are shortly described here.