Gap detection thresholds, defined by the minimum temporal disparity between the offset of one pulse and the onset of a second, were used to describe auditory temporal resolution. Temporal resolution, as defined by the gap threshold, was observed to decrease as the frequency disparity between the successive pulses increased. These results cannot be accounted for in terms of a simple temporal masking hypothesis. normal auditory function. APPARATUS Sinusoids were led from two audio oscillators (General Radio, Models 1302A and 1304B) through separate electronic switches (Grason-Stadler, Model 1229). The output of each switch was led to aprecIsIon attenuator (Hewlett-Packard, Model 350D), then to a mixer, amplifier, and impedance matching network, and finally to an earphone (TDH-49) which was located in an audiometric test chamber (Industrial Acoustic Co., Model 1200) where S Iistened. Programming was provided with a six-channel Teletype tape fed through a modified tape reader (Frieden, APT), which in turn set a logic control unit (BRS/Foringer, 200 series). The logic control unit operated the audio switches and