This article investigated the development of phonological encoding in speech production by examining the production of reiterant two-word sequences varying in phonological similarity. Two groups of typically developing children and a group of college-aged adults participated. Both groups of children produced target words with longer durations when they were preceded by words sharing initial consonant-vowel (CV) sequences than when preceded by phonologically unrelated words or words sharing vowel-consonant (VC) sequences. For adults, the duration of target words was shorter when they were preceded by words sharing final VC sequences than in the other conditions. The developmental decrease in the influence of CV-related prime words on target-word duration may be related to changes in the level of activation of lexical items during speech production. Developmental changes in the influence of VC-related prime words are less clear, but may be due to age-group specific behavior in the production of identical sequences of words.