Angiotensin converting enzyme (ACE) is well known for its dual actions in converting inactive Ang I to active Ang II and degrade active bradykinin (BK), which play an important role in the control of blood pressure. Since the bottle neck step is the production of pressor Ang II, this was targeted pharmacologically in 1970s and successful ACE inhibitors such as captopril were produced to treat hypertension. Researches on domain specific ACE inhibitors are continuing to produce effective hypertension controlling drugs with fewer side effects.