In 2009, the U.S. Supreme Court issued what many considered a seminal decision regarding the treatment of divisibility and apportionment in multi-party cases involving the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Liability in response actions brought under CERCLA section 107 is typically joint and several. On occasion, courts have allowed potentially responsible parties (PRPs) to argue that the harm is divisible and should be apportioned. In Burlington Northern & Santa Fe Railway Co. v. United States, the Supreme Court upheld the application of apportionment using multiple factors for divisibility. 556 U.S. 599, 614 (2009). A few courts had allowed apportionment in CERCLA cases prior to the Burlington decision but on a limited, single-factor basis. It was thought that Burlington might open the door to more expansive application of apportionment in multi-party CERCLA cases. Since Burlington, however, courts continue to conservatively apply apportionment in the CERCLA context. That said,Burlington together with subsequent CERCLA apportionment cases do provide some guidance regarding the principles that parties might apply when trying to make a successful apportionment argument.