An experiment conducted to compare the discomfort produced by whole‐body sinusoidal vibration with that produced by one‐third‐, one‐, and three‐octave vibration spectra is described. Seated subjects were required to adjust the level of a variable test vibration such that it produced a degree of discomfort similar to that caused by a 10‐Hz sinusoidal vertical whole‐body vibration at 0.75 m/sec2rms. The test stimuli were nine sinusoidal vibrations (at 3.15, 4.00, 5.00, 6.30, 8.00, 10.00, 12.50, 16.00, and 20 Hz); nine one‐ third‐octave bands of random vibration centered at the above frequencies, three single‐octave bands (centered at 4.00, 8.00, and 16.00 Hz) and a three‐octave band (centered at 8.00 Hz). The results obtained by this method indicate that the mean equivalent discomfort produced by all the random motions employed in the experiment may be predicted by weighting the vibration spectra with a filter network. A suitable filter response is that determined from a contour of equal comfort for sinusoidal or one‐third‐octave random vibration.Subject Classification: [43]65.70.