Using the Freedom of Information Act, the ACLU filed the request for documents Monday on behalf of six Islamic organizations and several individual Muslims.
Islamic leaders said the FBI gave them little information when they alleged that investigators had been monitoring local Muslims and mosques.
Shakeel Syed, head of the Islamic Shura Council of Southern California, said many area Muslims have reported being questioned by the FBI about sermons delivered in local mosques.
The government has 20 days to respond to the ACLU's request under the Freedom of Information Act. In an e-mail to the Los Angeles Times, FBI officials said they would address the request but did not say if they would turn over documents.
"The FBI does not investigate anyone based on their lawful activities, religious or political beliefs," said J. Stephen Tidwell, Assistant Director of the FBI's Los Angeles office.
Federal authorities have emphasized a commitment to build ties with Muslims and Arab group, partly to help with terrorism investigations, but recent disclosures of Bush administration domestic surveillance programs have strained those relationships.
"People are asking me if it is safe to worship," said Ranjana Natarajan, an attorney working on the FOIA request. "People began to worry that maybe there is something wrong with going to the mosque."