Clientelism is a central feature of politics in Solomon Islands and Papua New Guinea. Most voters vote in search of personalized or localized benefit, and most politicians focus on delivering benefits to their supporters at the expense of national governance. In this article, I explain how clientelism impedes development in both countries. I then describe underdevelopment's role in causing clientelism. I also explain the resulting trap: clientelism causes underdevelopment, and underdevelopment causes clientelism. Because of the trap, clientelism will shape the two countries' politics for the foreseeable future. However, the history of other countries gives cause to believe it can be overcome in the long-run. In the second half of the paper, I explain how change may occur. I also outline implications for aid policy, looking at how clientelism constrains the impact aid can have, and explaining how donors can act to maximize their impact in a difficult environment.