Acoustic analyses of the sibilant fricatives, [s, z, ∫, ȝ], produced in initial position before [a], [i], and [u] were performed. LPC spectra revealed reliable anticipatory vowel coarticulation effects, viz., spectral peaks affiliated with the second formant of the following vowel, present 30–60 ms before vowel onset. These peaks represent oral resonances excited by either aspiration or voicing and indicate that during the latter part of the fricative the constriction begins to open in anticipation of the vowel. Acoustic characteristics of the peaks varied with vowel context due to differences in the anticipatory coarticulation of each vowel. In the context of the high vowels, [i, u], both assimilation and articulatory overlap of the fricative and vowel configurations was evident from the frequencies of the clearly defined spectral peaks. However, in the [a] context the opposing configurations for the fricative constriction and the low back vowel, which are executed sequentially, resulted in poorly differentiated peaks. The data are congruent with perceptual evidence that high vowels are more accurately identified than low vowels in fricatives excised from fricative-vowel syllables, thus exemplifying links between articulatory, acoustic, and perceptual aspects of coarticulation.