The article explores how voluntary precautionary recommendations for cell phone usage influence people's health concerns and behavior. An experimental study using a sample of Swiss citizens (N= 408) was conducted. Three different versions of a newly developed booklet, which focused on common misconceptions in regard to mobile communication, and an existing booklet were tested. The experimental design addressed questions of the potential effects of knowledge, precautionary recommendations, and sender identity on health concerns and transfer of the proposed recommendations. Participants’ perceptions were measured three times: immediately before and after reading the booklet, and two weeks later. The reading of the booklets increased participants’ knowledge considerably and led to perceptual changes. In regard to cell phones, health concerns increased after the reading and stayed at a higher level even after two weeks. The negative perception of base stations, in contrast, tended to decrease. Neither the identity of the sender nor the omission of precautionary recommendations had significant effects on health concerns. Provision of specific recommendations enhanced readers’ behavioral changes. Confrontation with information per se, and not precautionary recommendations, influenced the public's health concerns. These changes should not prevent the provision of precautionary recommendations because, in the face of scientific uncertainty, these are the only means through which to enable users to make informed decisions.