This article addresses the most fundamental procedural issues arising from Arts. 13, 14, 15, 18 and 53(1), (2) and (4) of the ICC Statute (hereinafter “the Rome Statute” or “RS”). It first analyses the reasons why the proceedings provided for in those articles constitute, referred to in this article as “Triggering Procedure”, within the complex procedural system provided for in the ICC Statute, an autonomous procedure whose object, parties and proceedings are perfectly distinguishable from the object, parties and proceedings of the Criminal and Civil Procedures. Once the relationship between the Triggering Procedure and the Criminal and Civil Procedures is introduced, the article analyses the procedural treatment of the principle of complementarity in the different procedures provided for in the ICC Statute. Finally, the last part of the article brie fly addresses the key role of the Of fice of the Prosecutor in the Triggering Procedure, and the duties imposed upon the competent Chamber of the Court to control, propio motu or at the request of a party to the proceedings, that the Of fice of the Prosecutor is acting within the powers granted to it by the RS and fully respecting the substantive and procedural standards set out by the RS.