The present study aims at a precise topographic characterization of dynamic EMG-activity pattern in bilaterally recorded masseter and temporal muscles. EMGs were monopolarly recorded (62- channels, 10–700 Hz, 3000 samples/s, resolution of 2,44 mV/bit) by means of surface electrode arrays simultaneously with the acceleration of lower jaw in 25 healthy volunteers (age: 17–27 years). The EMGs were processed by a 20 Hz high-pass and a 50 Hz reject filter and quantified by calculating the root mean square (RMS). The RMS-time profiles were time-normalized and averaged as well as topographically analyzed by dynamic EMG maps. During the time course of chewing cycles the intramuscular EMG distribution changed. In the masseter muscle the EMG activity started in anterior-caudal regions whereas the further increase took place more in medial-caudal regions. In the temporal muscle the main activity shifted from posterior-caudal to anterior-cranial regions. The intramuscular differentiation between the measurement points increased up to the peak EMG activity. In comparison between working and balance side the RMS levels were much more different in the masseter than in the temporal muscle. Dynamic map sequences in correlation with the EMG-RMS profiles enable to visualize the inter- and intramuscular co-ordination processes.