Ethnic groups:
Persian 51%, Azeri 24%, Gilaki and Mazandarani 8%, Kurd 7%, Arab 3%, Lur 2%, Baloch 2%, Turkmen 2%, other 1%
http://www.cia.gov/cia/publications/factbook/geos/ir.htmlI had no idea - I thought Persians were the vast majority. How significant it is, I'm not sure; this is an article from the Asia Times, who are normally without bias:
The myth that Azeris in Iran constitute an oppressed minority has only held sway among extreme pan-Turkics in Baku and Ankara. Indeed, the realities of modern Iran depict a very different picture from that of pan-Turkic propaganda. While the total number of Azeris (including the 3-million-strong "Persianized" Azeri residents of Tehran) does not exceed 7 million, they have consistently punched well above their demographic weight. Azeris have dominated the modern Iranian military since its establishment in the 1920s. Moreover, a disproportionate number of Iranian political elites have hailed from the Azeri minority. This was the case with the former Pahlavi regime, just as much as it is the case with the Islamic Republic that succeeded it in 1979. Indeed, Iran's supreme leader Ayatollah Ali Khamenei is an ethnic Azeri and so is Rahim Safavi, the overall commander of the Islamic Revolutionary Guards Corps (IRGC) and the most important military-security official in the country.
http://atimes.com/atimes/Middle_East/FI28Ak01.html