This study quantitatively reviews the empirical studies of negative political advertising. A method of the combination of citation analysis and content analysis is used. The citation analysis examines each cited work in 20 selected studies with respect to its citation information; and the content analysis investigates these 20 selected studies (citing sources) in terms of their hypotheses, research questions, and methodologies. The aggregated information from the individual cited works and the citing works show that scholars from communication and other disciplines have strong influence on the development of the empirical studies on negative political ads, but communication scholars remain as the driving force. Facing continuously increased literatures in the area, communication scholars need to develop a theory or theories to guide the research. The direction of the research has been moving toward focusing on the boarder and more general effects of negative political ads.