Electromyograms (EMG) during Japanese and English word processing work with various keyboard heights was recorded and analyzed with amplitude probability distribution methods, in order to examine the effect of keyboard height on local muscular load in the shoulder and forearm regions. The EMG was recorded from the extensor carpi radialis brevis muscles, the trapezius muscles and anterior and medial portion of the deltoideus muscles. The keyboard height was placed at 5cm below elbow, elbow height, 10cm above elbow and height selected by the examinee. Eight young female students volunteered to participate in this experimental study. According to the results of the EMG amplitude probability distribution analysis, keyboard height gave different loads to the respective muscles. For example, the load to the extensor carpi radialis brevis muscles decreased as the keyboard position became higher, while the load of trapezius muscles increased. In conclusion, it was suggested that there is no best keyboard height during VDT work from the view point of muscles load. Therefore the keyboard height should be adjusted considering the characteristics of individual VDT work and the muscles fatigue of the operator.