Poststimulatory threshold shift has been measured for 1000‐cps stimuli of varying duration and sensation level, turned on and off either without audible transients or abruptly. The measurement was performed by means of test stimuli of varying duration and following the prime stimulus at various time intervals. The results show that the poststimulatory threshold shift depends little on the duration of the test stimulus, but that it depends critically on the time interval between the termination of the prime stimulus and of the test stimulus. The poststimulatory threshold decreases as this time increases. The poststimulatory threshold increases with sensation level and it depends in a complex fashion on the duration of the prime stimulus. The time pattern of the threshold changes radically when a gradual cutoff of the prime stimulus is replaced by an abrupt one. Replacing the 1000‐cps tone by a random noise leads to the same result as an abrupt cutoff.