This chapter explores developments in investor- state dispute settlement (ISDS) in the last year (January– December 2019) in relation to, on the one hand, jurisdiction and admissibility and, on the other, procedure and conduct. From determining the existence of a qualifying investment to the fate of jurisdictional objections relating to the recent Achmea judgment of the Court of Justice of the European Union (CJEU), and from arbitrator challenges to orders of provisional measures. The chapter addresses some important developments that have marked the most recent decisions of arbitral tribunals.