Questions probing subjective assessment of risk perception, level of anxiety, and ability to avoid flu infection were asked on a 9 point ordinal scale with anchors at the extrema (''very high'', ''very low'') and the center (''intermediate''). Subjective emotional status (i.e., respondents' affective state regarding the epidemic) was anchored by the terms ''very calm'' through ''intermediate'' to ''very anxious.'' Comparative questions of subjective risk percep-tion for eight health threats were asked using a five-point ordinal scale with anchors at all points: ''very low,'' ''low,'' ''intermediate,'' ''high,'' and ''very high.'' Questions regarding media (both respondents' frequency of getting information from a particular source and their judgment of each source's accuracy) were asked on a five point ordinal scale with anchors at all points (''very often/ accurate'' to ''never/almost certainly inaccurate''). Respondents' knowledge of swine flu was assessed with a series of six True/False questions. Respondents gave free-text responses to questions about their current age, the number of people currently living in their household (including themselves) and their zip code if they currently live in the United States. Respondents who reported not currently living in the United States were asked to report their current country of residence in a free-text field. A screen-shot of the full survey instrument is included in the Supplementary Material.