The effect of noise bandwidth on the acoustic-reflex threshold was studied in 12 normal-hearing adult subjects by independently varying the cutoff frequencies of low-pass (fL=100 Hz) and high-pass (fH=6000 Hz) computer-generated noises. Adjusting the cutoff frequency of the low-pass or high-pass activating stimuli over the 700–6000 Hz range resulted in a change in the reflex threshold of 4 dB/octave. As the cutoff frequency of the low-pass noise was reduced below 700 Hz, more rapid increases in reflex thresholds occurred. For high-pass stimuli, very small changes in reflex thresholds were noted as the lower cutoff frequency was increased from 100 to 700 Hz. The data suggest that between 700 and 6000 Hz equal spectral regions of a noise stimulus contribute equally to the reflex threshold, and that energy below 700 Hz contributes little to the sensitivity of the reflex.