To investigate the effects of whole body vibration on the central nervous system, rats were exposed to various whole body vibrations and changes in whole brain levels of Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were then determined. Changes in plasma corticosterone levels were also determined and related to the changes in the whole brain levels of 5-HT and 5-HIAA. The dose-related changes in the 5-HT and 5-HIAA levels were observed as acceleration increased from 0.4G to 5.0G. Changes in vibration frequency also affected the 5-HT and 5-HIAA levels of brain: they were significantly elevated at a frequency of 20 Hz (P less than 0.05). Plasma corticosterone levels increased as acceleration increased from 0.4G to 5.0G. As the vibration frequency was changed from 5 Hz to 30 Hz, plasma corticosterone levels also rose significantly (P less than 0.05) but the extent of elevation was approximately the same at each frequency. The correlation between brain 5-HT and plasma corticosterone levels with increasing acceleration (r = 0.93, P less than 0.01) was significant.