Gastric adenocarcinoma (GA) is a major tumor type of gastric cancers and subdivides into several different tumors such as papillary, tubular mucinous, signet-ring cell and adenosquamous carcinoma according to histopatholigical determination. In other hand, GA is also subdivided into intestinal and diffuse type of adenocarcinoma by the Lauren?fs classification. In this study, we have examined differential gene expression pattern analysis of three histologically different GAs of 24 samples by using DNA microarray containing approximately 19000 genetic elements. The hierarchical clustering analysis of 24 gastric adenocarcinomas (12 of intestinal type, 7 of diffuse type and 5 of mixed type) resulted in two major subgroup on dendrogram, and two subgroups included most of intestinal and diffused type of GAs respectively. Supervised analysis of 19 intestinal and diffuse type GAs by using Wilcoxon rank T-test (P<0.01) resulted in 100 outlier genes which exactly separated intestinal and diffuse type of GA by differential gene expression. In conclusion, genome-wide analysis of gene expression of GAs suggested that GAs may subclassify as intestinal and diffused type of GA by their characteristic molecular expression. Our results also provide large-scale genetic elements which reflect molecular differences of intestinal and diffuse type of GAs, and this may facilitate to understand different molecular carcinogenesis of gastric cancer.