The importance of the precautionary principle in public health was highlighted in France after the HIV contamination of blood products used for transfusion. However, the definition of this principle, its objectives, the way in which it should be applied, and its consequences had not been considered previously. The question as to whether the application of the precautionary principle is appropriate remains unanswered. The aim of this study was to analyze the interpretations of the application of the precautionary principle to determine its consequences in terms of risk management and patient rights. This was accomplished by interviewing persons involved in transfusion medicine. We conducted 33 interviews and describe the issues enunciated for and against the application of the precautionary principle. The precautionary principle concept was confusing to the respondents. A major issue emerging from the interviews was that the precautionary principle was perceived more as a means of protecting the decision maker than as a means of protecting the patient. Taken to its extreme, the use of the precautionary principle could prejudice sound medical decision making. However, it was felt that it also can lead to the introduction of measures that update and gradually reduce risks associated with transfusion.