The bimaterial constant e is necessarily used in the interfacial crack problems. Some authors tried to neglect the effects of the bimaterial constant e. To investigate the effects of the bimaterial constant e, the individual strain energy release rates,G I * andG II *, which are obtained by neglecting the bimaterial constant e, are examined. Three examples were investigated to see the importance of the effects of the bimaterial constant e. Firstly, the analytical results of a center interfacial crack between two dissimilar materials in an infinite plate are illustrated for various loading conditions. The phase angles of a center interfacial crack are also examined to check the importance of the bimaterial constant e. Secondly, the individual energy release rates of a center crack paralleling an interface are examined. Thirdly, the finite element results of a four-point bending beam with two symmetrical cracks paralleling an interface are illustrated. Considering the analytical and numerical results, we can see that the bimaterial constant e is an important factor in the interfacial crack problem, which can not be neglected.