The present union certification system has many faults, the most important of which is its failure to deliver employee representation to all but a small and declining minority of workers. As an alternative, compulsory proportional representation (CPR) would have many advantages, particularly when compared with other reform proposals, most of which are designed to only reinvigorate, modify, or supplement the existing system. Would CPR have any disadvantages? We identify four potential concerns: reduced freedom to contract, increased interunion competition and raiding, depleted union strength, and compromised union independence. However, we argue that some of these problems would be more imagined than real, some less serious than expected, and some would have secondary effects to compensate any shortcomings.