Phonological development in children is described in terms of four stages; (1) preverbal vocalization and perception (birth to 1;0); (2) phonology of the first 50 words (1;0 to 1;6); (3) phonology of simple morphemes (1;6 to 4;0); and (4) completion of the phonetic inventory (4;0 to 7;0). (CTM)