The objective of the preliminary research to be described is to quantify the psychophysical similarity of vowel‐like stimuli that differ in certain spectral and waveform characteristics. To that end, the vowel /æ/has been synthesized by adding together sinusoidal harmonics of the appropriate frequencies, amplitudes, and phases. Changes to these parameters and to fundamental frequency are made on a period‐by‐period basis. The resulting synthetic waveform is essentially indistinguishable from that produced by a conventional cascade formant synthesizer, but the present synthesis technique permits the experimenter to manipulate certain spectral and temporal details more easily. A set of 65 different vowels acoustically similar to /æ/have been synthesized by manipulating formant frequencies, formant bandwidths, spectral tilt, phase relations among harmonics, and filtering passband/stopband. Subjects are asked to estimate the psychophysical distance between each stimulus and a reference vowel in a 380‐trial randomized test. Results will be discussed in terms of various theories of vowel perception. [Research supported in part by an NIH grant.]