The purpose of this study was to evaluate the interrelationships between the maxillary and mandibular edentulous ridges and to compare the posterior tooth position in complete dentures made by outside dental offices, “used denture”, to those made by the dental laboratory of our dental college hospital, the “new denture”.Copy dentures of each new and used dentures were made from plaster. After the measuring points were established, the moire topographic photographs were taken and then traced. Data of the width of the overlapping residual ridge crest zone, vertical dimension of inter residual ridge crest and the angle of inter residual ridge crest line were statistically analyzed. A personal computer was used for measuring the bucco-lingual distance between the measuring points of the copy denture and the bisecting the crest of the residual ridge and/or the overlapping residual ridge crest zone.In this investigation, it is suggested that the overlapping residual ridge crest zone is a suitable criterion for the arrangement of artificial posterior teeth for complete dentures. Although the statistical analysis indicated that there were no significant differences in the mean distance between the used denture and the new denture, the authors felt that the former was wider than latter.