The purpose of this study was to obtain preliminary data concerning the acoustic‐phonetic structure of speech produced under high sustained acceleration. Acoustical measurements were made of a set of Air Force vocabular words as spoken by two subjects at 1 g and 6 g's. There were differences in both the durational and spectral characteristics of speech, though not always consistently for the two speakers. At 6 g's, vowel formants tended to centralize, and fundamental frequency in stressed syllables increased for both speakers. For one speaker, word durations increased consistently under acceleration while for the other speaker, the durational differences were inconsistent. Duration differences were primarily a function of changes in vowel duration. [Sponsored in part by the Air Force Office of Scientific Research/AFSC, United States Air Force, under Contract F49620‐85‐C‐0013.]