The present study was carried out to investigate the relationships between the depth of overbite and the masseteric silent period Normal subjects of 44 were selected, which consisted of 9 open bites, 24 normal overbites and 11 deep bites, all were 19-29 years of age EMG activity was recorded on the bilateral masseteric muscles and craniofacial radiography was done. The following results were obtained 1. The mean duration of masseteric silent period was 18.58±4.50 msec in open bite, 17.37±7.05 msec in normal overbite and 19.30±7.62 msec in deep bite groups. 2. There were no significant differences on masseteric silent period among open bite, normal overbite and deep bite groups. 3. There were no significant correlations between masseteric silent period and craniofacial variables.