While reviewing the grounds of the administrativeact, administrative courts shall issue acancellation decision in case they determinethat the grounds presented by the administrationto be based on the administrative acthas not been materialized. However, despiteof this determination, will the administrativecourts be able to reach the opinion that theadministrative action is legitimate because ofanother grounds for the administrative act thatthey have found ex officio and refuse the claimant'sclaim?Contrary to what is generally considered, isthe substitution of grounds in the administra- tive jurisdiction procedure an activity that canonly be carried out on the grounds of the ad- ministrative act? Instead of the grounds of theaction laid down by the plaintiff, shall the courtbe able to render judgment based on the factu- al reasons that the court has found ex officio?While trying to find answers to thesequestions, we will encounter some proceduralrules that add originality to administrativejurisdiction procedure. The inquisitorialprocedure, the prohibition of extendingor amending of allegation and defense (inthe meaning of administrative jurisdictionprocedure), and the procedural rules regardingcourt's inability to making decision on behalfof the administration lead us to in-depthdeliberation in the discussion on substitutionof grounds. The possible effect of substitutionof grounds in administrative jurisdictionprocedure on the principle of contradiction(the right to fair trial), the protection of thepublic interest, and the principle of the rule oflaw have always become the major issues thatare taken into consideration throughout thestudy.