An Iranian employed by the British embassy has gone on trial along with a French woman and dozens of moderates accused of inciting unrest after the presidential election in Iran.
It is the second such hearing. Proceedings started against 100 people last week.
The opposition has dismissed the hearings as a show trial.
State media said an Iranian employee of the French embassy, was also in the dock, as was French teacher Clotilde Reiss, 24.
The BBC reports she was stopped on 1 July as she prepared to leave Tehran, having spent five months as a university teaching assistant.
She is accused of "collecting information and provoking rioters" and has been charged with acting against national security,
The Irna news agency said she told the court that she wrote a one-page report about the situation in Isfahan and gave it to the French embassy's cultural section.
Ms Reiss reportedly told the court she regretted taking part in the protests.
The French government has demanded Iran immediately release the two women.
The EU has warned Iran the trials will be considered an action against all of the European Union and treated accordingly.
The election on 12 June saw President Mahmoud Ahmadinejad returned to power, but opposition leaders insist the election was rigged. At least 26 people have been killed and hundreds arrested in unrest since then.