The complexity of Alzheimer's disease (AD) has made it difficult to examine its underlying mechanism. A gene microarray offers a solution to the complexity through a parallel analysis of most of the genes expressed in the brains from AD-transgenic mice. In our previous study, a total of 52 differentially expressed genes were identified in 18-month-old APPsw-transgenic mice compared to age-matched normal mice. We extended our work to better understand the relevant gene profiles from both early- and late-stage transgenic and normal mice. To accomplish this, cDNA microarray was used with the large-scale screening of the brain mRNA from transgenic and normal mice of 1 and 18 months of age. We identified a total of 48 genes, 6 up-regulated and 42 down-regulated, differentially expressed with a significant degree of induction and reduction in the brains from moderate 18-month-old transgenic mice compared to 1-month-old transgenic mice. In parallel, a total of 40 differentially expressed genes, 6 up-regulated and 34 down-regulated, were also found in the brains from moderate 18-month-old normal mice compared to 1-month-old normal mice. Thus, differentially expressed genes upon APPsw overexpression and the aging process are useful targets through which investigators can choose genes of particular interest. In the future, it will be necessary to study the function of differentially expressed genes, which are targets for developing drugs, using pharmacoproteomics.