The contributions in this volume are based on an analysis of data from bilingual children acquiring French and German simultaneously. The longitudinal studies started at approximately 18 months and continued until age six. The papers focus on the development of specific grammatical phenomena. Explanations are given within the framework of the "Principle and Parameter" approach. The study is primarily concerned with the acquisition of so-called "functional categories" and the consequences of their acquisition for the development of grammar. Specific points dealt with in these papers include: gender, number and case and their internal structure (DP versus NP), inflection and its consequences for agreement marking, and word order phenomena (subject-raising constructions, including passives, and word order in subordinate clauses). The basic hypothesis underlying this study is that early child grammars consist only of lexical categories and that functional categories are implemented later in the child's grammar. How this happens exactly is the central issue explored in this book.