Recently, a reluctance of lay and medical personnel to perform mouth-to-mouth resuscitation (MMR) in hospital and community settings has been documented, with 45% of respondents declining to perform MMR on a stranger. In the present study, we examined whether the perceived risk and fear of contracting infectious diseases diminishes the willingness of paramedics and emergency medical technicians (EMTs) to perform MMR. Seventy-seven EMTs and 27 paramedics responded to a questionnaire, administered by one of two physicians, containing mock cardiac arrest scenarios that were designed to assess willingness to perform MMR as a citizen responder. Faced with a situation in which an adult stranger required MMR, 57% of the participating EMTs and all of the paramedics stated that they would refuse to perform MMR. None of the paramedics and only 32.5% of the EMTs stated that they would perform MMR on a man in a gay neighborhood. In addition, 23% of the EMTs and 37% of the paramedics indicated that they would refuse to perform MMR on a child. White respondents were more willing than nonwhite respondents to perform MMR. Twenty-nine percent of the prehospital-care providers had been in situations requiring MMR in the community, and 40% either had walked away or did only external compression. Of those participating paramedics and EMTs who had performed MMR in emergency situations, only 45% indicated that they would do so again. The respondents indicated that they would not be willing to administer MMR because of the fear of contracting infectious agents, especially the human immunodeficiency virus. Despite the proven effectiveness of MMR in saving lives, paramedics and EMTs are highly reluctant to perform MMR as citizen responders. Their perceived risks of contracting infectious agents during MMR are high, despite the low actual risks. We recommend that instruction in cardiopulmonary resuscitation for providers of pre-hospital care, the medical community, and the general public should emphasize the benefits of providing MMR, the actual low risks of contracting infectious diseases during administration of MMR, and the use of widely available and effective barrier masks to minimize any risks due to administration of MMR.