By Jon Leyne
BBC News, Tehran
Iran has been marking the anniversary with 10 days of celebrations
Iran is marking the 30th anniversary of its Islamic revolution.
It will be celebrated in a big rally in central Tehran expected to be addressed by President Mahmoud Ahmadinejad.
On this day three decades ago, the last resistance of the Shah's regime collapsed. Iranians spilled out on to streets to celebrate their new freedom.
But three decades on, Iran is still suffering major economic problems, international isolation, and complaints about the lack of political freedom.
There will be plenty of celebrations on Tuesday, but also - less openly - plenty of criticisms as well.
Iran has certainly achieved full independence, but at the expense of continued international isolation.
Political and personal freedom is restricted. The economy is in a mess, through a combination of mismanagement and sanctions.
Many Iranians struggle to survive.
The new administration in Washington offers the possibility of a new beginning.
But President Ahmadinejad's government has so far been reluctant to move away from the reassuring rhetoric of "Death to America".