Social perception and the construction of social reality are intrinsically linked. This study tested the conjoint effects of participant rationality and two story attributes, severity and context, on perception of the SARS threat and on story evaluation. Participants’ rationality was assessed by the Rational-Experiential Inventory. Stories of SARS were manipulated to be either severe or non-severe, and with or without context. Two experiments using identical manipulations and measurement instruments were conducted, one in the US and one in China. Among high rationality individuals, contextual information was effective in assuaging apprehension, but only in China where the perceived threat was serious. However, story attributes consistently affected story evaluation. Findings were discussed in terms of how rationality affected health information processing in response to changes in perceived risks and how story attributes contribute to the effectiveness of health communication. Implications for social construction of health risks were then offered.