1. An Overview of Research on Bilingualism.- 1.1 The Definition of Bilingualism.- 1.2 Previous Research.- 1.3 Description of the Present Research.- 2. Word Acquisition.- 2.1 The First Stage: The Bilingual Child Has No Equivalents.- 2.2 The Second Stage: The Child Begins to Build a System of Equivalents.- 2.3 Does the Bilingual Child Have Twice as Many Words as the Monolingual Child?.- 2.4 Summary.- 3. Development of Basic Sentence Structure.- 3.1 Sentence Structure Analysis.- 3.1.1 The Nuclear Sentence.- 3.1.2 The Amplified Nuclear Sentence.- 3.1.3 The Complex Nuclear Sentence.- 3.1.4 Binuclear Sentences.- 3.2 Results.- 3.2.1 The First Stage.- 3.2.2 The Second Stage.- 3.2.3 The Third Stage.- 3.3 Summary.- 4. Several Aspects in the Acquisition of Morphology and Syntax.- 4.1 Verb Tenses and Conjugations.- 4.2 Past Perfect.- 4.3 Intralanguage Hypercorrection.- 4.4 "Mistakes" of Agreement.- 4.5 Diminutive and Augmentative.- 4.6 Articles.- 4.7 Participle and Infinitive.- 4.8 Pronouns and Gerunds.- 4.8.1 Omission of the Pronoun.- 4.8.2 Use of the Gerund.- 4.9 Understanding Subtle Differences.- 4.10 Superextension of Forms into Both Languages.- 4.11 Negation, the Adjective, the Possessive, and Subject-Verb Inversion.- 4.12 Word Order.- 4.12.1 Two-Word Sentences.- 4.12.2 Participial.- 4.12.3 Subordinate Clauses.- 4.13 Summary.- 5. Interferences.- 5.1 Definitions.- 5.2 Lexical Interferences.- 5.3 Morphological Interferences.- 5.4 Interferences in Word Order.- 5.5 Semantic Interferences.- 5.6 Phonological Interferences.- 5.7 Summary.- 6. A Bilingual Upbringing.- 6.1 The First Stage: The Role of the "Sole" Interlocutor.- 6.2 The Second Stage: The Child Begins to Speak the Language of the Majority.- 6.2.1 An Educational Tactic: "What Did You Say? I Didn't Understand ".- 6.2.2 A Natural Strategy.- 6.2.3 A Request That is Destined to Fail: "Say It in English".- 6.3 The Third Stage: The Maintenance of Bilingualism.- 6.4 Summary.- 7. Conclusions.- References.