Genomic research that is part of current DNA sequencing projects is having a great impact in many fields of study. With the discovery of sequence information for human and mouse genomes, an explosion of genetical and functional data will be revolutionizing mechanistic studies of hypertension syndrome. Assuming the availability of genome sequences, the challenge includes identifying genes, predicting the proteins they encode, determining when and where genes are expressed and how they interact, and learning how these expression and interaction profiles change in response to environmental signals. As the hypertension research community enters the post-genome era, the study of gene expression patterns and phenotypes in model animals will be a part of analyzing the role of genes involved in the pathogenesis of hypertension. The molecular dissection of hypertension genetics is a complex multidisciplinary challenge and a medical imperative. The understanding of complex disorders such as hypertension has advanced considerably through the use of genetically engineered mice. Studies of hypertension using transgenic and knockout mice have uncovered multiple potential functions of the regulatory systems controlling blood pressure. In this review, I discuss the molecular basis of the hierarchy and network of genomic expression cascades of hypertension by focusing on the functional significance of the renin-angiotensin system.