Vowel production is only rarely considered in discussions of articulation disorders, and the most widely used clinical tests of articulation provide only minimal evaluation of vowel articulation. Indeed, even the literature devoted to the mastery of vowel production by children without articulation disorder is limited, although several recent studies have demonstrated that vowel acquisition does not occur as easily or as early as had been suggested. The subject for the study reported here is an 8-year-old boy diagnosed with developmental apraxia of speech who has been treated for his speech difficulties since the age of 2 years 10 months. At this time his speech is intelligible, although still distorted. This study will evaluate his vowel production in two ways. First, listeners will identify words from minimally contrastive word sets; this to allow us to examine his ability to produce distinctively different and identifiable English vowels. Second, measurements will be made of vowel duration for English long-short vowel pairs and formant frequency for the ten English simple vowels. The latter will be compared to the children's formant frequency data reported by Peterson and Barney [G. E. Peterson and H. L. Barney, J. Acoust. Soc. Am. 24, 175--184 (1952)].