The impetus for this book on evaluation in the library context sprang from a poster session presented at the 1997 American Library Association Conference in San Francisco. Entitled, "Siren Song: The Lure of Technology and the Betrayal of Reality", the poster session focussed on teaching the need to evaluate information found on the Internet. This book affords us the opportunity to call upon several of the pioneers in Web source evaluation. The result is this collection of contributions from individuals who present their best thinking on the subject.