Since the 1970s, US law has made military assistance conditional on the human rights record of recipient governments. The prospect of receiving US military aid would, in principle, create an incentive for states to respect rights. This study assesses whether US military aid has exercised the hoped-for positive influence on human rights in recipient countries, a question for which no published research exists. The analysis of data from over 150 countries covering thirty years indicates that US military assistance is associated with worse performance on human rights.