Promising effects in mice of immunization by ß-amyloid stimulated substantial research efforts and high hopes. In retrospect, this study appears simultaneously logical, consistent as it is with the amyloid theory central today in the field of Alzheimer's disease studies, and paradoxical, because it involved using the toxic substance itself for a treatment benefit. The research thus begun opens up multiple perspectives for experimentation and for treatment. Clinical trials began, but had to be stopped in January 2002 because of serious side effects. The editors' objective for this book is not to arouse false hopes for a therapeutic project that must still be proven, but to discuss the available information and the questions it raises.