Compositions and methods are provided for the modulation of abnormal expression of &bgr;-amyloid. oligonucleotides are provided which are specifically hybridizable with RNA or DNA encoding &bgr;-amyloid. Oligonucleotides specifically hybridizable with a translation initiation site, codon 717, codon 670 or codon 671 of RAPP are provided. Such oligonucleotides can be used for diagnostics as well as for research purposes. Methods are also disclosed for modulating &bgr;-amyloid expression in cells and tissues using the oligonucleotides provided, and for specific modulation of expression of the mutant RAPP gene. Methods for diagnosis, detection and treatment of diseases associated with abnormal &bgr;APP expression are also disclosed.