Government
Type: Islamic republic.
Constitution: Ratified December 1979, revised 1989.
Branches: Executive--"Leader of the Islamic Revolution" (head of state), president, and Council of Ministers. Legislative--290-member Islamic Consultative Assembly (Majles). Judicial--Supreme Court.
Political parties: The following organizations appeared to have achieved considerable success at elections to the sixth Majles in early 2000: Assembly of the Followers of the Imam's Line, Freethinkers' Front Islamic Iran Participation Front, Moderation and Development Party, Servants of Construction Party, and Society of Self-sacrificing Devotees.
Administrative subdivisions: 28 provinces.
Suffrage: Universal at 15.

Government of Iran
The December 1979 Iranian constitution defines the political, economic, and social order of the Islamic republic. It declares that Shi'a Islam of the Twelver (Jaafari) sect is Iran's official religion. The country is governed by secular and religious leaders and governing bodies, and duties often overlap. The chief ruler is a religious leader or, in the absence of a single leader, a council of religious leaders. The constitution stipulates that this national religious leader or members of the council of leaders are to be chosen from the clerical establishment on the basis of their qualifications and the high esteem in which they are held by Iran's Muslim population. This leader or council appoints the six religious members of the Council of Guardians (the six lay members--lawyers--are named by the National Consultative Assembly, or Majles); appoints the highest judicial authorities, who must be religious jurists; and is commander in chief of the armed forces. The Council of Guardians, in turn, certifies the competence of candidates for the presidency and the National Assembly.

The president of the republic is elected by universal suffrage to a 4-year term by an absolute majority of votes and supervises the affairs of the executive branch. The president appoints and supervises the Council of Ministers (members of the cabinet), coordinates government decisions, and selects government policies to be placed before the National Assembly. The National Assembly consists of 290 members elected to a 4-year term. The members are elected by direct and secret ballot from among the candidates approved to run by the Council of Guardians. All legislation from the assembly must be reviewed by the Council of Guardians. The Council's six lawyers vote only on limited questions of the constitutionality of legislation; the religious members consider all bills for conformity to Islamic principles.

In 1988, Ayatollah Khomeini created the Council for Expediency, which resolves legislative issues on which the Majles and the Council of Guardians fail to reach an agreement. Since 1989, it has been used to advise the national religious leader on matters of national policy as well. It is composed of the heads of the three branches of government, the clerical members of the Council of Guardians, and members appointed by the national religious leader for 3-year terms. Cabinet members and Majles committee chairs also serve as temporary members when issues under their jurisdictions are considered.

Judicial authority is constitutionally vested in the Supreme Court and the four-member High Council of the Judiciary; these are two separate groups with overlapping responsibilities and one head. Together, they are responsible for supervising the enforcement of all laws and for establishing judicial and legal policies.

The military is charged with defending Iran's borders, while the Revolutionary Guard Corps is charged mainly with maintaining internal security. Iran has 28 provinces, each headed by a governor general. The provinces are further divided into counties, districts, and villages.
source: http://www.state.gov