This is the most influential body in Iran and is currently controlled by conservatives. It consists of six theologians appointed by the Supreme Leader and six jurists nominated by the judiciary and approved by parliament.
Members are elected for six years on a phased basis, so that half the membership changes every three years.
The council has to approve all bills passed by parliament and has the power to veto them if it considers them inconsistent with the constitution and Islamic law. The council can also bar candidates from standing in elections to parliament, the presidency and the Assembly of Experts.
Reformist attempts to reduce the council's vetting powers have proved unsuccessful and the council banned all but six of more than 1,000 hopefuls in the 2005 elections.
Two more, both reformists, were permitted to stand after the Supreme Leader intervened. All the female candidates were blocked from standing.