This study examined the responses of small primate, the squirrel monkey, to acute exposures to hyperdynamic environments. Body temperature, heart rate, and behavior of four restrained squirrel monkeys were recorded. After baseline monitoring at 1 G, monkeys were exposed to: a) +2 Gz for 60 min, b) a hyperdynamic profile simulating the gravitational envelope of the space shuttle during launch (8 min, +2.9 Gz max), or c) a simulated shuttle re-entry profile (19 min, +1.7 Gz max). In all experiments, the colonic temperature started to fall within 10 min of the onset of centrifugation and declined by as much as 2 degrees C in some conditions. This was in contrast to the stable body temperature observed during the baseline period. Also, the heart rate showed distinct elevations during centrifugation. Heart rate subsequently declined to baseline levels during the post-centrifugation phase. Behaviorally, after the onset of centrifugation, the animals periodically appeared to become drowsy and fall asleep. On the other hand, during the control period they tended to be alert, shifting their gaze about the cage. Thus, primates are susceptible to acute exposures to hyperdynamic fields, demonstrating significant physiological and behavioral changes.