Twenty-five women with breast implants participated in semistructured interviews designed to reveal their "mental models" of the processes potentially causing local (ie, nonsystemic) problems. The authors analyzed their responses in terms of an "expert model," circumscribing scientifically relevant information. Most of the women interviewed had something to say about most elements in the expert model. Nonetheless, gaps in their mental models undermined decision making about their implants. One woman misunderstood the terms used by the medical community to describe implant failure (eg, rupture, leak, and bleed). Another exaggerated the implants' vulnerability to direct impacts, such as car accidents. Participants also overestimated their ability to detect localized problems and to select medical remedies. Although they were generally satisfied with their own implants, many participants were dissatisfied with the decision-making processes that lead to their choice. Their interviews are interpreted by the form and content of communications that women with implants need to help them manage their health decisions better.