The cultural cognition thesis holds that individuals form risk perceptions that reflect their commitments to contested views of the good society. We conducted a study that used the dispute over mandatory HPV vaccination to test the cultural cognition thesis. Although public health officials have recommended that all girls aged 11 or 12 be vaccinated for HPV-a sexually transmitted virus that causes cervical cancer-political controversy has blocked adoption of mandatory school-enrollment vaccination programs in all but one state. An experimental study of a large sample of American adults (N = 1,538) found that cultural cognition generates disagreement about the risks and benefits of the vaccine through two mechanisms: biased assimilation, and the credibility heuristic. We discuss theoretical and practical implications.