The use of police informants and undercover officers in the United Kingdom is controlled under the Regulation of Investigatory Powers Act (RIPA) 2000. Prior to RIPA, the gathering of information through secretive means--such as surveillance, listening devices, the interception of communications, and the use of informants--was not subjected to sufficient safeguards, which led to a series of embarrassing judgments against the UK Government in the European Court of Human Rights. RIPA does not provide a complete framework for covert investigations, so it is supplemented by codes of practice, a series of statutory instruments, and the Police Act 1997. Codes of practice address the interception of communications, property interference, covert surveillance, and covert human intelligence sources. Oversight of RIPA is the responsibility of the Chief Surveillance Commissioner and the Interception of Communications Commissioner, both of whom must have held high judicial office. Their responsibility is to keep under review the performance of functions under Part III of the Police Act 1997 and the performance of the powers and duties conferred or imposed by or under Parts I-III. In addition to the commissioners, a tribunal has been established under RIPA s. 65 in order to deal with complaints under s.7(1)(a) of the Human Rights Act 1988. This chapter describes authorization procedures under RIPA for the use or conduct of an information source. Topics addressed include the duration of authorizations, review, renewals, and cancellations. The management of informers is also considered. Other issues discussed are the security and welfare of informants, informants and undercover officers involved in the commission of crime, fair trial values, human rights, the potential for abuse, and the admissibility of evidence. 31 notes and 38 references