SUMMARY. This study is concerned with the development of the ability to make a simple phonetic analysis of the spoken word. It describes the performance of children a t different levels of mental development on the task of analysing word sounds into two components : a letter sound and a sound unit which is the residual word obtained by elision of the letter sound from the test word. The results, which refer to the mental age range 5+ to 9+, suggest that there is a gradual progression towards accurate phonetic analysis, in the course of which children :(a) Come to recognise that words and sounds are interrelated. These necessary features of the ability are not attained in discrete, successive steps, but are present in increasing proportions with advancing mental age. Mental age 7+ is indicated as the level a t which they first become available in sufficient degree to permit some success with the task.exla.