Subjects were exposed indoors to simulated sonic booms having outside overpressures of 50 and 150 N/m z. Rise times were held constant at 5.5 ms. In addition to the outside measurements, inside measures of dB (lin) and dB (A) were also obtained. Subjects attempted to hold a hand-steadiness device on target during boom exposure and amplitude of the armhand startle response was determined. Recordings were also obtained of the skin conductance and heart-rate responses as well as the eye-blink reflex. A!!hough the 50 N/m 2 boom produced slight arm-hand startle responses in a small percentage of subjects, the frequency of these responses was significantly greater to the higher boom level. There Was no difference 9 9 t between the levels m amphtude of the response. The predommant autonomic response pattern to the lower exposure level was similar to that obtained for Orienting responses, while a startle pattern was obtained for the higher level. The results are compared with the findings of other studies and the following conclusions advanced 9 Sonic booms experienced indoors can cause slight arm-hand startle responses which could have adverse effects on occupational tasks in which arm-hand steadiness is the principal skill required. However, there is little evidence ttiat these responses significantly impair performance on less sensitive psychomotor tasks. It should be emphasized that these conclusions are based upon laboratory or semi-laboratory (field) studies, and that, because of differences in subject expectancies, the startle reactions could be more pronounced under "real-life" conditions 9