This chapter addresses one of the crucial tensions facing modern investment arbitration: that between confidentiality and privacy, on the one hand, and transparency and inclusiveness, on the other. It begins by reviewing how investment arbitration frameworks have addressed this tension so far, noting the traditional focus on confidentiality and privacy and the more recent trend towards transparency and inclusiveness of proceedings before ICSID and/or NAFTA tribunals. The chapter then compares domestic public law approaches to questions of transparency and public interest representation. Having reviewed US, English, French, German, and Greek law, it shows that domestic public law seems to accept the principle of transparency and provides for various forms of indirect public interest representation (e.g., through amicus curiae briefs) but also different forms of public interest claims. While this approach cannot be directly transposed to investment arbitration, it clearly can, and arguably should, guide the approach of investment lawyers.