Previous research has shown a difference in vowel acoustics between older and younger adults, possibly related to age-related changes in vocal tract morphology. Other data suggest that vowel acoustics may vary as a function of neighborhood density and word frequency in older adults, possibly due to the mediating influence of lexical access. This investigation examined whether these two factors interact. Results show that older adults had overall lower-frequency formants, and qualitatively different-shaped vowel spaces, than the younger adults, but the influences of word frequency and neighborhood density on the acoustic characteristics of vowels were statistically equivalent in both groups.