This thesis is an investigation of whole-body vibration exposures in forestry skidders. A six, degree-of-freedom calibration procedure was developed to calibrate six degree-of-freedom motion sensors. This calibration was applied to the sensors used to simultaneously measure accelerations at the seat/operator interface and chassis of forestry skidders. The results of this study indicate that skidder seats amplify the whole body vibration accelerations at the seat/operator interface when compared to corresponding chassis values. The acceleration values outlined in this study are similar to those published over the past twenty years suggesting that little has changed with respect to the ability of the seat to attenuate harmful vibration. To our knowledge, this thesis represents the most comprehensive six degree-of-freedom field data set collected and analyzed to date for any type of off-road vehicle.