Thousands of Iranians gathered outside the former US embassy in Tehran to mark 25 years since 52 Americans were held hostage in the Islamic Revolution.
Speakers linked the protest to Iran's pursuit of nuclear technology
Demonstrators, chanting anti-US and anti-Israeli slogans, linked the protest to international pressure over Iran's nuclear programme.
Militant students seized the US embassy - described as the "nest of spies" - in 1979 and held it for 444 days.
The hostage-taking has soured relations between the US and Iran ever since.
The incident was a turning point in a revolution which toppled the pro-US shah in Iran. Diplomatic ties between the two nations were severed in 1980.
The protest by mainly young Iranians came as US President George W Bush's camp claimed victory in the race for the White House.
Demonstrators paraded a giant Uncle Sam effigy and beat a puppet of Mr Bush with a shoe, as well as burning the Star and Stripes.
The crowd was told this was a symbol of Iran's freedom from oppression, rather than aimed at the US people.
Protesters said they feared strikes on Iran if Bush was re-elected
Teenagers chanted slogans like "Death to Israel and the corrupt culture of the West" and "Down with the USA and death to America".
But the BBC's Frances Harrison in Tehran notes that most demonstrators were not even born at the time of the embassy siege and several knew the building only by its post-revolutionary name, the "den of spies".
Speakers linked the anniversary protest to the growing controversy over Iran's nuclear programme.
They praised Iran's parliament for backing the government's pursuit of nuclear technology, including uranium enrichment.
Some in the crowd said they feared a Bush victory would increase the likelihood of a military strike against their country.
On Monday, hundreds of students demonstrated at the Atomic Energy Organisation building in Iran to show their support for Tehran's nuclear programme.