The study evaluated whether durational and allophonic cues to word boundaries are intrinsic to syllable production, and so acquired with syllable structure, or whether they are suprasyllabic, and so acquired in phrasal contexts. Twenty preschool children (aged 3 ; 6 and 4 ; 6) produced: (1) single words with simple and complex onsets (e.g. "nail" vs. "snail"); and (2) two-word phrases with intervocalic consonant sequences and varying boundary locations (e.g. "this nail" vs. "bitty snail"). Comparisons between child and adult control productions showed that the durational juncture cue was emergent in the four-year-olds' productions of two-word phrases, but absent elsewhere. In contrast, the allophonic cue was evident even in the three-year-olds' productions of single words. Perceptual judgments showed that age- and type-dependent acoustic differences translated into differences in listener behavior. The differential acquisition of the two juncture cues is discussed with reference to the acquisition of articulatory timing control.