Using a unique dataset composed of female employees at a large medical organization, this paper explores the role of social interactions among female co-workers and neighbors in the decision to obtain breast cancer screening exams. In our theoretical framework, the experience of other women is salient because it alters the tolerance for ambiguity about their own vulnerability, via a comparative ignorance effect. We find that the social multiplier ranges from 2 to 3: the equilibrium effect of an exogenous shock that impacts the probability of performing a mammogram is two to three times the shock itself. We perform a number of checks: among other things, these reveal (in agreement with the model and our intuition) that such a social effect is stronger for women whose job (according to the O*NET dictionary of occupations) offers more opportunities for social interaction, and weaker for individuals directly involved in health care, such as doctors and nurses.