The latency of acoustic reflex and reflex decay were studies in 23 normal adults using Virtual 310(version 4.4) digital impedance audiometry. The latency of acoustic reflex was defined as the period showing initial 10% of reflex after the sound stimulation(LI : initial latency). The reflex decay was recorded for 20 seconds using ipsilateral continuous stimulation according to the frequencies and intensities. The following results were obtained : 1) The LI(mean±SD) in the 500Hz were 35±56 msec in the reflex threshold level and 64±86 msec in the 5dB above threshold level. In the 1,000Hz the LI was 84±94 msec in the threshold and 143±86 msec in the 5dB above threshold level. In the 2,000Hz the LI was 138±123 msec in the threshold and 150±89 msec in the 5dB above threshold level. 2) As the frequencies were increased, the latency of the acoustic reflex was significantly increased(p<0.01). 3) The acoustic reflexes in the 500Hz were decayed 17±16% during the first 5 seconds, 21±16% in 10 seconds, 23±19% in 15 seconds and 26±16% in 20 seconds, respectively. In the 1,000Hz, the reflexes were decayed 25±34% in 5 seconds, 30±31% in 10 seconds, 36±29% in 15 seconds and 39±30% in 20 seconds. In the 2.000Hz, the reflexes were decayed 29±25% in 5 seconds, 39±27% in 10 seconds, 46±29% in 15 seconds and 53±29% in 20 seconds. 4) For 20 seconds of stimulation sound, the reflex decays were 52% in 500Hz, 65% in 1,000Hz, 96% in 2,000Hz. So the more increment of frequency and duration of stimulation sound is, the more chance of reflex decay is in normal adults.