Accumulating evidence indicate that various growth-related genes, growth factors and extracellular matrix components play a central role in the pathogenesis of cardiovascular and renal diseases by regulating cellular phenotype, growth and migration or promoting tissue fibrosis. Treatment of hypertensive rats with an angiotensin II type 1-receptor (AT1-receptor) antagonist normalizes cardiac phenotypic modulation and the increased fibrosis-related gene expressions in hypertrophied heart, leading to the improvement of cardiac dysfunction. The AT1-receptor antagonist can inhibit protooncogenes (c-fos, c-jun and Egr-1) and fibronectin gene expressions in rat balloon-injured artery, which is associated with the inhibition of neointima formation. Furthermore, the AT1-receptor antagonist prevents either the phenotypic modulation of glomerular mesangial cells or the increase in transforming growth factor-β1 expression in nephrosclerosis. Thus, the AT1-receptor antagonist in vivo potently inhibits the expression of growth-related gene and extracellular matrix and inhibits cellular phenotypic modulation. The AT1-receptor is responsible for the pathogenesis and development of cardiovascular and renal diseases.