Existing case-study research suggests that the recent increase in human rights violations in Latin America is attributed to the US-funded drug war. This narrative, which is referred to as the collateral damage perspective, stands in contrast to US human rights law, which makes governments' respect for human rights a precondition to receive aid. The apparent endogeneity between aid and human rights introduces bias that casts serious doubts on the validity of the collateral damage narrative. In addressing endoge- neity, this article presents a simultaneous instrumental variable analysis of the human rights effects of US counternarcotic aid in the Americas. The results show that while counternarcotic aid to regimes increases overall violations of human rights, this effect is greater among democracies than autocracies. And with the exception of torture, this fi nding is consistent when disappearances, political imprisonment, and extrajudicial killings are also considered. The implication of this research suggests that policy makers in Washington risk losing regional support for US drug control policies if US laws that govern the allocation of aid are not effectively implemented. The impact of US counternarcotic aid in facilitating the escalation of drug- related violence and human rights violations in Latin America is highly contested. Recent reports of the bodies of mutilated and decapitated victims of the drug war have grabbed the attention of the media, human rights groups, and policy think tanks (Amnesty International 2008; Molzahn, Rios, and Shirk 2012). Human rights groups claim that the escalation of drug-related violence, especially in Mexico and Colombia, and extrajudicial killings of citizens at the hands of their governments in the execution of the drug war are in large part a function of collateral damage by US fi nancial sponsorship of drug enforcement in the region (Amnesty Interna- tional and Fellowship of Reconciliation 2008). A burgeoning academic literature has found support for this collateral damage narrative. Recent empirical research shows that US drug enforcement policies and sponsorship of the drug war in Central America and the Caribbean produced the unintended effect of increasing levels of property crime and violent crime (Bartilow and Eom 2009a). Case studies show how US counternarcotic aid to democratic governments in Latin America has also produced the unintended effect of increasing human rights violations. In other words, the narrative that emerges is that as US counternarcotic aid interacts with the democratic institutional characteristics of recipient governments that are engaged in the execution of the drug war, it degrades respect for human rights (Youngers 2005; Bagley 1992; Crandall 2008; Craig 1980). This narrative, however, stands in direct contradiction to US human rights law. The Leahy Amendment (or Leahy's Law), passed by Congress in 1997, prohibits