Throughout the debate in the United States Congress over whether vaccines cause autism, legitimizing symbols that index cultural values have played a prominent role in the establishment of credibility. While both sides sanctify the role of science in producing credibility, they draw on different images of what science is and where its legitimacy stems from. Those who favor the vaccine hypothesis frame science as a populist endeavor, the results of which are open to critique by all. Those against the vaccine hypothesis frame science as an elitist endeavor, the results of which may only be critiqued by fellow scientists. While both of these images derive their significance from the cultural history of the United States, they have a markedly different impact on the interpretation of evidence. From within the populist frame, personal experience and direct observation are highly valued. From within the elitist frame, epidemiological evidence trumps personal experience. Due to the incorporation of dueling images of science, the US debate over autism may be viewed as a debate between rival cultural values.