Various studies have revealed apparent motoric compensation between articulatory structures such as the jaw and lips which contribute to articulatory goals of vocal tract constriction. The present study, like Perkell et al. [J. Acoust. Soc. Am. 93, 2948-2961 (1993)] and Savariaux et al. [J. Acoust. Soc. Am. 98, 2428-2442 (1995)], investigates the possibility of compensation between labial protrusion and constriction and dorsovelar constriction-a relationship based on the similarity of the acoustic effects of such articulatory goals. The present study differs from these earlier studies in that it assumes an articulatory model of gestures, and it examines nonperipheral back vowels. X-ray microbeam records of American English speakers producing back vowels under various stress conditions were investigated. Results reveal systematic speaker differences in the direction of correlation between measures of labial and dorsal position. These results show that speakers differ as to whether they exhibit coupling between labial and dorsal activity in the lowering of back vowel timbre.