The nOtiOn Of 「 ' SiZe effeCt " iS Shown tO COntain inherent COnCeptUal diffiCU 且 tieS. A neW framework to be called 「 ' shape effect theory " , incorporating 卜 鬮 shape ' 鬮 as a key variable in place of " size " , is proposed to overcome those Clifficulties . Several cases of pullout rupture of concrete anchors and flexural rupture ofbeams are analyzed satisfactorily using this frarne − work . Furthe ore , a hypothesis of " hidden dimensions " is proposed to alert to a possibility that an apparent size effect that is really a shape effect is related to some hidden dimensions in the object that are ignored in the theoretical model used for observation . Keywords: size effect, shape effect , volume effect , brittle fracture , pullout rupture , flexural rupture