The OIC comprises 57 states dispersed over four continents, spanning from Albania (Europe) in the north to Mozambique (Africa) in the south, and from Guyana (Latin America) in the west to Indonesia (Asia) in the east.
But, despite its size, which includes nearly one-third of the members of the United Nations, its numerous committees and the scope of its stated activities, the OIC is run on a shoe-string budget.
The supreme body of the OIC is the Conference of Heads of State, which convenes every three years. The first summit conference, held in Rabat in 1969, decided that member states would "consult together with a view to promoting close cooperation and mutual assistance in the economic, scientific, cultural and spiritual fields, inspired by the immortal teachings of Islam".
In the interval between summits, OIC foreign ministers meet to oversee the implementation of decisions taken by the heads of state. The first foreign ministers' meeting took place in 1972, when the OIC Charter was adopted.
However, the day-to-day running of the OIC is left to the Secretariat, which consists of a secretary-general and four assistant secretaries-general.
Secretary-general: Ekmeleddin Ihsanoglu
Ekmeleddin Ihsanoglu, an Egyptian-born Turkish former diplomat, succeeded Morocco's Abdelouahed Belkeziz as the OIC leader at the end of 2004. He promised to "re-energise" the organisation by making administrative changes.
Turkey had lobbied hard on behalf of its candidate, presenting Mr Ihsanoglu as a reformer, both in terms of the OIC and the wider Islamic world.
Mr Ihsanoglu has called for collective action by Islamic countries to combat religious extremism. He wants a greater role for Muslim nations in international affairs, including permanent representation in the UN Security Council.
The secretary-general is elected by the Conference of Ministers of Foreign Affairs for a four-year term, renewable once. Mr Ihsanoglu is the first head of the OIC to have been chosen by secret ballot.
Although a useful forum for discussion, the OIC lacks the means to implement its resolutions, which often remain as unheeded declarations.
Thus, despite a 1981 call to redouble efforts "for the liberation of Jerusalem and the occupied territories" and to institute an economic boycott of Israel, several members, including Indonesia, Egypt, Jordan and Arab Gulf states, maintain economic ties with Israel.
Furthermore, pledges for financial aid to member states or to Muslim communities suffering from civil war or natural disasters are often at best met only in part.
As a broad organisation whose member states are widely dispersed geographically, the effectiveness of the OIC has also been constrained by the fact that many of its members have a wide variety of political orientations, from revolutionary Iran to conservative Saudi Arabia. Members have sometimes been in bitter dispute with one another, such as Iraq and Iran and Iraq and Kuwait.
While the net effect of these differences is often weak resolutions or ones that are honoured only in breach, sometimes they result in the boycott of summit conferences altogether, such as happened in 1991, when 12 Arab heads of state failed to turn up in Senegal in protest against the presence of Jordan and the Palestine Liberation Organisation, which had taken Baghdad's side in the war which followed Iraq's invasion of Kuwait.