This publication presents four studies which represent recent core work of the OECD Investment Committee. The first study, "Transparency and Third Party Participation in Investor-to-State Dispute Settlement ," aims to enhance understanding of the role of transparency and third party participation in investor-state dispute settlement procedures. It examines the current rules, steps taken to improve transparency, and the perceived advantages as well as the challenges of additional transparency.  Two other studies touch upon two of the most frequently contested provisions in investor-state arbitration. "Fair and Equitable Treatment Standard in International Investment Law" clarifies the concept, based on jurisprudence and state practice. "‘Indirect Expropriation’ and the ‘Right to Regulate’ in International Investment Law" identifies the main criteria found in investment agreements and used by tribunals to articulate the difference between the two concepts.  The final paper looks at most favoured nation treatment.