In designing an automobile seat, it is important to minimize the fatigue experienced by the driver resulting from long-term sitting. We have utilized the following measurement techniques to quantify driver fatigue during actual road-test conditions. (1) subjective evaluations of fatigue based on multi-dimensional scaling; (2) measurement of body movement by an electromagnetic field transducer; and (3) electromyographic recordings (EMG) of muscle activity. These methods were used during four hour driving tests involving five subjects in each of four seats which differed in design. For each subject, a weighted fatigue index based upon responses to a questionnaire was calculated. Body movement was analyzed by using a position transducer attached near the iliac crest. The EMG median freqency and amplitude were analyzed for eight muscles of the back. By recording these measurements simultaneously, we have provided a means of comparing subjective indices of driving fatigue with objective physiological parameters.