This overview illustrates that there is a gap in our knowledge of how domestic courts handle investor-State disputes. As it turns out, some foreign investors use the domestic courts of the host State prior to initiating investment treaty arbitration. Subject matter-wise, these cases are very diverse and not all of them are initiated by investors against the host State. Moreover, in the four countries analysed, investors often appealed to the highest courts of the land, but they lost more cases than they won. These findings should help UNCITRAL Working Group III conceptualize the meaning of “investor-State dispute” and the relationship between domestic and international methods of ISDS. This overview concludes by inviting further empirical research to understand how domestic courts handle investor-State disputes. This in turn can help us develop normative arguments as to why domestic courts should be included in the reform process.