One of the most common features of international investment treaties is the obligation of a state to grant ‘fair and equitable treatment’ to investors and investments. Treatment giving rise to allegations of breaches of this obligation has taken many forms, namely bad faith, discrimination, denial of justice, frustration of legitimate expectations, lack of transparency, coercion and harassment, and arbitrariness or arbitrary conduct. This latter form of treatment – arbitrariness – has rarely been the focus of scholarly works and, thus, its scope and meaning are difficult to ascertain. When examined in the context of international investment disputes, however, one may conclude that, while its scope and meaning may vary, arbitrariness is indeed a legitimate basis for claim under the fair and equitable treatment standard. The thresholds for demonstrating arbitrariness, however, are decidedly and consistently high.