This study is a guide to all aspects of the methodology of child language research, and to its conceptual and historical background. It explores from first principles such issues as the competing merits of naturalistic and controlled observation, the selection of research subjects, and the collection and analysis of data. The book brings together the different contributions of the two disciplines - psychology and linguistics - which lay claim to child language research, disciplines which are diverse in their methods and often incompatible in their theoretical goals. Illustrating its argument in detail with examples from commonly cited books and articles, the book evaluates those methods and theories which best allow the process of language acquisition to be discovered, described and, ideally, explained. It concludes the discussion with an historical survey of the content and methods of child language research since 1970.