Differential gene expression between normal breast epithelial cells and the malignant counterpart was studied using microarray technique. We utilized GeneAlbum GEM 1-6 from Incyte Pharmaceuticals, Inc., which contains which contains 65,873 cDNA clones (57,172 clones excluding controls), representing 33,515 individual genes. The normal human mammary epithelial cells (HMEC) from 3 donors were used to search different gene expression patterns among individuals, ages and races. In addition, 8 well-established breast cancer cell lines were used as probes against a common normal HMEC from 50 years old donor