The invention provides compositions and methods for the treatment of diseases associated with amyloid deposits of Aβ in the brain of a patient, such as Alzheimer's disease. Such methods entail administering an immunogenic fragment of Aβ, lacking a T-cell epitope, capable of inducing a beneficial immune response in the form of antibodies to Aβ. In another aspect, the immunogenic fragment of Aβ is capable of elevating plasma Aβ levels. The immunogenic fragments comprise linear or multivalent peptides of Aβ. Pharmaceutical compositions comprise the immunogenic fragment chemically linked to a carrier molecule which may be administered with an adjuvant.