Recent investigations raise questions about the temporal development of tuning in the auditory system [S. P. Bacon and B.C. J. Moore, J. Acoust. Soc. Am.80, in press (1986)]. They demonstrated that simultaneous masking psychophysical tuning curves (PTCs) were broader, on the high‐frequency side, when the probe tone coincided with masker onset that when it was temporally centered in the masker. We replicated their experiment in normal‐hearing listeners and extended it to hearing‐impaired listeners who demonstrated abnormal PTCs. Simultaneous PTCs for 10 dB SL 20‐ms probe tones, masked by 400‐ms masking tones, were obtained with the probe at the onset and at the temporal center of the masker. Results from normal‐hearing listeners confirmed earlier findings. However, in hearing‐impaired listeners there was little change in PTC shape with temporal position. These data suggest that the mechanism responsible for the temporal effect in normal ears are ineffective in listeners with sensorineural hearing loss. [Work supported by NINCDS.]