Early results on synthetic‐vowel formant amplitude discrimination by Flanagan [J. Acoust. Soc. Am.27,1223–1225 (1955); J. Speech Hear. Disord.22,205–212 (1957)] indicated that ΔIfor overall vowel level was about ± 1.5 dB, but that ΔIforF2 was about ± 4 dB. The latter result was forF2 ≃ − 12dBre: F1 for the “comparison” vowel. Subjects made a same‐different judgment which may have affected the interpretation of these results. Here we report ΔIfor several “comparison” vowels which differ in amplitude relations amongF1,F2, andF3. In addition, we report on perception of extreme shifts in formant amplitude, Implications for computer recognition of speech will be discussed.