The first oral direct renin inhibitor, aliskiren, recently received approval for 
the treatment of hypertension. This article addresses the premise, promise, and 
potential limitations of this new class of renin-angiotensin system inhibitor. 
Although aliskiren adds to a list of more than 100 drugs approved for the 
treatment of hypertension, its introduction into clinical medicine is of 
particular interest because of the novel mechanism of action: inhibition of 
renin's catalytic activity, the most proximal and rate-limiting step in 
renin-angiotensin system activation. By producing more complete 
renin-angiotensin system inhibition than with existing agents, direct renin 
inhibitors may afford greater protection from hypertensive complications. Other 
potential advantages include additional blood pressure reduction when used in 
combination therapy, a placebo-like side-effect profile, avid renal 
concentration, and long duration of action. Potential limitations include modest 
levels of blood pressure reduction that are equivalent to but not greater than 
angiotensin receptor blockers, reduced gastrointestinal absorption with a 
high-fat meal, and large reactive increases in renin secretion--the functional 
importance of which is under intense investigation. The results of outcomes 
trials are eagerly awaited.