When synthetic fricative noises from an [s] continuum are followed by [a] and [u], adult listeners perceive fewer instances of in the context of the rounded vowel [u] (Mann & Repp, 1980). This perceptual context effect presumably reflects adjustment for certain coarticulatory effects and implies tacit knowledge of coarticulation and its consequences. To clarify the role of articulatory experience in the ontogeny of such knowledge and the consequent perceptual adjustment, the present study examined the effect of rounded and unrounded vowels on the perception of [s] and by adults, 5-, and 7-year-old children who produce and [s] and 7-year-old children who misarticulate these phonemes. All three groups of children showed a context effect equivalent to that of adults and independent of age and articulation ability. Therefore, productive mastery of [s] and is not critically responsible for perception of the [s] distinction, nor for perceptual sensitivity to the consequences of sibilant-vowel coarticulation.