This chapter describes the development of proactive investigation in Belgium itself, its regulation and organization, and the ongoing reform debate as it has been fuelled by new scandals. It addresses cross-border proactive investigations from a Belgian perspective. In the meanwhile, privacy concerns had made an inroad into Belgian doctrine and case law, particularly under the influence of the European Court of Human Rights. In a number of high profile cases the Belgian criminal justice system had already shown some distressing malfunctioning. Difficult and sensitive entirely national proactive policing and undercover investigations might be the difficulties and dangers multiply when the Belgian borders are crossed. Belgian police officers have often been active promoters of international cooperation and the federal government has joined them. Understanding doctrine, any activity of foreign services on Belgian soil is conditional upon approval by the Belgian authorities.