In conclusion, we have applied the fluorescent differential method and the PPAR alpha-null mouse model for the rapid isolation of expression tags of PPAR alpha target genes that are involved in the action of peroxisome proliferators and in the regulation of lipid homeostasis under energy deprivation. Identification of a wide spectrum of PPAR alpha target genes will provide new insights into the diverse cellular pathways regulated by these receptor, and this information will be critical for understanding the complicated biological interactions among members of the PPAR alpha target genes. With the recent technological advancement, a newer method, such as DNA microarray, has emerged in the identification of differential gene expressions. This new DNA microarray method, in conjunction with the differential display method, is the first important step toward understanding the molecular mechanisms of gene interactions in any biological systems and can speed up the search for differential gene expressions.