This article discusses the covert surveillance of post and telecommunications as a coercive measure in Swiss criminal proceedings. Since such surveillance interferes with a number of fundamental rights and freedoms, it should meet the requirements of human rights limitations. Firstly, the offence must constitute a so-called “catalogue offence” under Art. 269 para. 2 of the Swiss Code of Criminal Procedure. Further, there must be a strong evidence to suspect that such a catalogue offence has been committed in reality. In addition, the seriousness of the offence must justify the surveillance. Finally, previously undertaken investigative activities must have proven to be unsuccessful, or there are grounds to suspect that in absence of such surveillance the investigation will not succeed or will likely become disproportionately more complicated. Against this background, the authors analyze the latest amendments to the Federal Statute on the Surveillance of Post and Telecommunications (the BÜPF) and their impact on the conduct of criminal proceedings.