The purpose of this report was to document phonological changes in a pair of identical twin boys diagnosed as language delayed. The boys were not enrolled in direct treatment, but were evaluated four times between the ages of 3;5 and 4;9. Speech samples were analyzed for phonetic inventories, phonological process use, and syllabic shapes. Observed changes in their speech generally followed normal developmental patterns.

Very little is known about the vowel systems of phonologically disordered children. This study provides longitudinal data regarding vowel use of identical twin boys between the ages of 3;5 and 4;9. The boys were identified as phonologically disordered; however, their parents chose not to enroll them in therapy. Vowel-use information was taken from spontaneous language samples. It was discovered that initially their phonological disorder also affected their vowel systems, but as their phonological skills increased so did correct use of vowels and their vowel use tended to follow normal developmental trends.