This study is based on a record of my daughter Joan's speech from her eleventh to her thirty-sixth month. It will deal chiefly with phonemic and lexical matters. For, apart from other reasons which will be discussed below, the morphological and syntactical development in the language of English-speaking children has been well described in numerous works, while only two authors have hitherto been concerned, implicitly or explicitly, with problems of phonemics in infant language, and as regards vocabulary patterns, it is impossible to glean any information from the customary alphabetical word lists.