HIS iS an account of the phonetic aspects of how one small boy learned 1 to speak his native English. The subject was born 1b, January, 1941, in New York City. In September, 1942, he was moved to a suburb of Philadelphia, where he has lived since. At the time of writing (April, 1945) he is fairly healthy, nervous, over-active, self-assertive, frequently 'difficult,' garrulous, and gregarious. His principal associates have been his father, mother, and mother's uncle. All are college-educated New Yorkers. Their speech is normal, with the following differences: The mother's uncle consistently 'drops r's' and uses [3I] in words like bird. The mother has had speech-training and done speech-teaching. Her usage in words like ask and words with final and preconsonantal r's is erratic. She says [sk] or [ask], [bad] or [bsd]. The father spent many of his formative years in Upstate New York and California, and consistently sounds final and preconsonantal r's. The child's speech may have been retarded by whooping-cough at the age of one, and by being, during the subject period, an only child. His passive vocabulary developed normally, and by the end of his second year he is believed to have understood several hundred words. At 12 months his babble consisted of repetition of several simple open syllables: [amarUa], [papapa], [gulguJgu], [rUlrUirgi], etc. The consonants were [r], [v], [;], [Ji], [j], [9]. The vowels were [i], [wI], and a variable low vowel [iJa/a/e], here transcribed [a]. The syllable [nJa] is believed to have signified annoyance and [pa] contentment. [i:] was a cry of pleasure. By 18 months he had added [b], [m], [n], [k], [d] and [w]; also a back round vowel varying from [X] to [u]. At 20 months he tried a wordv car [ka], but after a few trials dropped it and did not take it up again for several months. His next attempt was gone [g(n)], in which the second element varied from [U] to [o] and the third, when present, might be [n], [m], or [u]. For three months this word constituted his entire vocabulary. He used it frequently and always appositely. Between 18 and 24 months he added [h], [p], [t], and [s]. He dropped [tu] and the palatal and labiodental stops and nasals. The low vowel narrowed its range of variation down to [a/a]. The back-round vowel split into two: [o/3] and [o/ouXu]. At 23 months his babble was varied to include alternations of syllables: [gogugogu], [dadidadi], [aiaioi], [uiuiui]. He had added the following words: hole [ho(u)], meow (cat) [iau], woof-woof (dog) [?U?U], moo (cow)