Based on novel data from 48 semi-structured interviews, this book identifies four pathways through which counsel influence outcomes in investment treaty arbitrations. First, counsel establish facts and frame the case through evidence collection, witness testimony, and cross-examination. Second, they shape results through strategic selection of party-appointed and presiding arbitrators. Third, while advocacy's potential impact is significant, its practical impact is often limited due to its inconsistent quality. Fourth, counsel have a profound impact on the valuation of damages. They exert this influence indirectly by selecting and instructing valuation experts. In turn, these experts' influence derives from the combination of complex, speculative valuation analyses and arbitrators who struggle to understand and apply these analyses properly. Counsel may also exert significant direct influence in this area through their advocacy and cross-examination. This title is also available as open access on Cambridge Core.