Amidst threats of pandemic avian influenza and bioterrorist attack, public health surveillance and preparedness have never been more important. Early detection of biological events, electronic reporting of laboratory test results, efficient exchange of case reports across jurisdictions, and timely alerting of health threats are critical components of effective health protection. Essential to public health surveillance and preparedness is the timely availability of information relating to individuals? healthcare behaviors and clinical conditions -- posing a threat to personal privacy. Public health is challenged to maintain an optimal balance between protecting the nation?s health and respecting the personal privacy of its citizens.