Objective: This study was designed to measure the ability of listeners with and without sensorineural hearing loss to discriminate silent gaps between noise band markers of different frequencies presented in an anechoic and a reverberant listening environment. Design: A two-interval, two- alternative, forced-choice paradigm was used to measure gap discrimination ability for six listeners with normal-hearing and six listeners with sensorineural hearing impairment. Marker stimuli were narrow bands of noise centered at frequencies from 500 to 7000 Hz. The center frequency of the leading marker was held constant at 2000 Hz and the center frequency of the trailing marker was varied randomly across runs. Stimuli were presented in two virtual listening environments (anechoic and reverberant). The listeners' task was to indicate which interval contained the marker pair separated by the larger silent gap. Gap discrimination was measured as a function of the center frequency of the trailing marker and as a function of listening environment. Results: Gap discrimination thresholds (msec) varied as a function of the center frequency of the trailing marker. As the trailing marker frequency increased above and decreased below the leading marker frequency (2066 Hz), gap thresholds increased significantly. Hearing loss and listening environment did not have a significant effect on gap discrimination thresholds. Analysis of the gap discrimination functions revealed significantly steeper slopes for trailing marker frequencies below 2000 Hz than for trailing marker frequencies above 2000 Hz. A possible age effect was observed in the data and significant correlations were found between age and function slopes for several conditions. Conclusions: Gap discrimination becomes more difficult as the frequency disparity between leading and trailing noise bands increases. This pattern of results occurs independent of hearing loss but may be influenced by listener age.