Changes of interarch distance and condylar position related to loss of the posterior occlusal support were investigated. Five subjects, whose mandibular premolars and molars needed to be restored, were selected. Their experimental prostheses were removed in sequence from the most posterior to anterior. The more the posterior occlusal support decreased, the more the interarch distance in the first molar region decreased. When the occlusal supports of both mandibular molars and premolars were absent, the condylar position moved superio-anteriorly. The occlusal support of the first molar showed a significant role in maintaining the intercuspal and condylar position.