The mediating role of decision rights exercise effectiveness. Interdepartmental knowledge overlaps influence ISD performance primarily because they it influences how effectively the two classes of project decision rights are exercised during the ISD process. Higher technical knowledge in the client department facilitates better exercise of decision rights pertaining to project ratification and monitoring activities. Client technical knowledge therefore improves ISD efficiency because it enhances DCR exercise effective-ness. Similarly, higher business application domain knowledge in the IT unit lowers the likelihood of misconstruing the client department’s needs and making project implementation decisions that are inconsistent with the client’s objectives; i.e., it enhances the exercise of decision rights associated with project initiation and implementation activities. Such knowledge therefore improves ISD effectiveness because it enhances DMR exercise effectiveness. The foregoing logic leads to the final set of hypotheses.