Pharmacological interruption of angiotensin II type-1 (AT1) receptor signalling in animals with an ongoing nephrogenesis produces specific renal abnormalities characterized by papillary atrophy, abnormal wall thickening of intrarenal arterioles, tubular atrophy associated with expansion of the interstitium, and a marked impairment in urinary concentrating ability. Similar changes in renal morphology and function develop also in mice with targeted inactivation of genes encoding renin, angiotensinogen, angiotensin-converting enzyme, or both AT1 receptor isoforms simultaneously. Thus, an intact signalling through AT1 receptors is a prerequisite for normal renal development. Given the important role for renal-specific mechanisms in determining the level of arterial pressure, it is reasonable to expect changes in long-term arterial pressure following kidney maldevelopment. Indeed, both clinical investigations and experimental studies suggest that a diminished number of nephrons is related to the development of hypertension. There is accumulating evidence suggesting a role for the renin-angiotensin system in programming of adult arterial pressure through angiotensin II effects on developing and /or mature kidneys. Moreover, the RAS appears to have a dual effect on establishment of adult blood pressure, depending on the time periods of angiotensin II inhibition.