Liability management exercises (LME) have emerged as the latest trend in the restructuring industry due to a confluence of factors in the corporate credit market, judicial system and macro-economy. Creditors have pursued an array of solutions to avoid LME—namely adding covenants that block them in credit agreements for newly issued debt. For debt that has already been issued, lenders have only one option to regain negotiating leverage and avoid coercive exchanges—the cooperation agreement (Co-Op). This paper discusses the history of LME and Co-Ops and employs an event study to determine the impact of lender Co-Ops on the value of the firm. The event study determines the abnormal return from a Co-Op in a firm’s debt and equity securities. The study finds no statistically significant cumulative abnormal returns (CAR) following the signing of a Co-Op. It does find significant negative returns for equity prices in the Week +1 to Week +2 period. Together, the conclusions from the event study empower quantitative argumentation on the Co-Op’s compliance with the Rule of Reason framework under Sherman Antitrust Law.