In November 1986, the government reported that the preliminary count in the fourth national census, which had been conducted during October, showed a total population of 48,181,463. According to the government, this total included about 2.6 million refugees who had come from Afghanistan and Iraq since 1980. The population of Iranian nationals, around 45.6 million, described an increase of about 12 million over the 33.7 million enumerated in the 1976 census. This suggested that the Iranian population had grown at an annual rate of 3.6 % between 1976 and 1986. A population increase in excess of 3.3 % per year puts Iran's population growth rate among the higher rates in the world.

Iran is a multilingual and various cultural society, and the majority of the population is extremely young. Nearly one-half of the people speak Farsi, and another one-fourth speak some other Indo-European language or dialect. These are descendants of the Aryan tribes, whose origins are lost in antiquity. The Kurds, whose language has seen scant modification over the centuries, are a fierce nomadic people dwelling in the western mountains of Iran and in Iraq and Turkey. They constitute a small %age of Iran's population. They have resisted the Iranian government's efforts, both before and after the revolution of 1979, to assimilate them into the mainstream of national life. Also inhabiting the western mountains are seminomadic Lurs, thought to be the descendants of the aboriginal inhabitants of the nation. Closely related are the Bakhtyari tribes, who live in the Zagros Mountains west of Esfahan. Both speak Luri, a language distinct from, but related to, Farsi. The Baluchi are a smaller minority who inhabit Iranian Baluchistan, which borders on Pakistan.