Purpose: To examine the role of phonotactic probabilities at the onset of language development, in a new language (Dutch), while controlling for word position. Method: Using a nonword imitation task, 64 Dutch-learning children (age 2;2-2;8 [years;months]) were tested on how they imitated segments in low- and high-phonotactic probability environments, in word-initial and word-final position. The relationship between phonological representations and vocabulary development was examined by comparing children's performance with their receptive and expressive vocabularies. Results: Segments in high-phonotactic probability environments were at an advantage in production, in both word-initial and word-final position. Significant correlations were found between vocabulary size and children's mean segment repetition accuracy for word-initial position, but not in word-final position. Conclusion: The results indicate that phonological representations are mediated not only by children's developing vocabularies but also by the structure of children's emerging lexicons.