Notwithstanding the two decades that have passed since the implementation of Law Number 5 on the Prohibition of Monopolistic Practices and Unfair Business Competition in 1999, the Indonesian Competition Authority or Komisi Pengawas Persaingan Usaha ("KPPU") continues to face profound difficulties in uncovering cartel activities and thus in imposing penalties. Therefore, the KPPU strives to use circumstantial (indirect) evidence in its judicial practice to prove cartel transgressions. In German Cartel Law, EU Competition Law and in the US Antitrust practice, the courts also employ indirect (circumstantial) evidence, namely 'facilitating practices' and 'plus-factors', to substantiate cartel infringements. This book compares the different approaches to implimenting indirect (circumstantial) evidence in the Indonesian Competition Law to the German and European Competition Law, both from a procedural as well as a substantial law perspective.