A longitudinal electromyographic study of the anterior temporal and masseter activity during habitual chewing of apple was performed on 21 subjects provided with immediate complete dentures. At the pretreatment stage, when the patients having an anterior residual dentition were chewing, the peak mean voltages showed low values (range, 48 to 58 microV). After denture placement, there was a further decrease of the temporal activity that persisted to the 6-month stage. After the dentures were relined, a significant increase in chewing force of the temporal muscles was noted at the 1-year stage. During the second year, when no corrections of the dentures were made, the temporal activity decreased below the pretreatment level. The masseter muscle chewing activity generally showed no significant changes during the 2-year observation period. The mean durations of the chewing strokes and chewing cycles were longer than values reported in dentate samples and generally displayed no significant changes during the 2-year period.