In this article I demonstrate the knowledge perceptions of and the preventive health behaviors toward the influenza A H1N1 pandemic, or "human swine flu," among the chronic renal disease patients in Hong Kong. Based on ethnographic data from participant observation in a chronic renal disease patient self-help alliance and semistructured interviews with its 30 members, I demonstrate that the participants' knowledge perceptions of and the adoption of the preventive health behaviors against H1N1 were greatly influenced by their past experiences of being stigmatized in the 2003 severe acute respiratory syndrome (SARS) outbreak. In addition, the past experiences in the SARS outbreak not only led the participants to remember their stigmatization experiences in this H1N1 pandemic, but also aroused the memory of the general Hong Kong population that chronic renal disease patients were "dangerous" and "polluted," which could further contribute to their stigmatization in this H1N1 pandemic.