An electromyographic analysis of the buccinator muscle was undertaken, by use of surface electrode. Electromyograms were made from 30 subjects with normal dentition during various oral activity, The results were as follows; 1. No buccinator activity was elicited during slowly opening and closing the mouth. 2. The majority of subjects showed buccinator activity while biting hard, protracting the mandible, and retracting the mandible. 3. The buccinator muscle was found to be markedly and consistently active during swallowing, blowing, sucking and masticating. 4. The buccinator activity during pulling the lips against the teeth was of equal potential with pulling the lips laterally. 5. The buccinator muscle on the working side was more active than the buccinator muscle on the balancing side.