The indictment paves the way for Italy to try the Americans, along with five Italians, in June in the first criminal trial over the CIA's extraordinary rendition program.
But prosecutors believe that many of the American names in the indictment are aliases, and even if Italy requests the Americans' extradition a move that would strain U.S.-Italian relations it is unlikely that the agents, who have all left Italy, would be turned over for prosecution.
All the U.S. agents have court-appointed lawyers, who say they have had no contact with their clients. In Italy, defendants can be tried in absentia.
The CIA did not comment Friday on the case, which has put an uncomfortable spotlight on intelligence operations and increased U.S.-European disagreement over combatting terrorism.
Prosecutors allege that five Italian intelligence officials worked with the Americans to abduct Osama Moustafa Hassan Nasr from a Milan street on Feb. 17, 2003.
Nasr was allegedly taken to the Aviano Air Base near Venice and then flown to the Ramstein Air Base in southern Germany and onward to Egypt, where he was held for four years and, according to his lawyer, tortured. He was freed earlier this week by an Egyptian court that ruled his detention was "unfounded."
The Swiss government this week approved prosecutors' plans to investigate the flight that allegedly took Nasr over Swiss air space from Italy to Germany. And a German prosecutor recently issued arrest warrants for 13 people in connection with the alleged CIA-orchestrated kidnapping of a German citizen.
Italian prosecutors say the alleged kidnapping operation was a breach of their country's sovereignty that compromised Italy's own anti-terrorism efforts.
Nasr, who had the status of political refugee in Italy, was under investigation for terrorism-related activities at the time of his abduction, and Milan prosecutors issued a warrant for his arrest more than two years after he disappeared from Milan, while he was in Egyptian custody.
British opposition Conservative lawmaker Andrew Tyrie, head of a parliamentary group investigating allegations into CIA flights, said he hoped the criminal trial would expose those involved in the "repugnant practice" of rendition, or moving terrorism suspects from country to country without public legal proceedings.
Subjects of rendition have said they were tortured in the countries to which they were transferred.
"If British and European governments do not want to face the embarrassing prospect of being shown to have kept the public in the dark about rendition, they had better come clean on what they know, and fast," Tyrie said.
The Italian government this week asked the country's Constitutional Court to rule on whether prosecutors overstepped their bounds by wiretapping phone conversations of Italian secret service agents.
The government has said it will wait for a ruling which could suspend the trial even before it starts to respond to prosecutors' request to extradite the agents.
All but one of the Americans have been identified as CIA agents, including the former Milan station chief Robert Seldon Lady and former Rome station chief Jeffrey Castelli. The other is Air Force Lt. Col. Joseph L. Romano III, who was stationed at the time at Aviano.
Among the Italians indicted by Judge Caterina Interlandi was the former chief of military intelligence, Nicolo Pollari, and his former deputy, Marco Mancini. Pollari has denied any involvement by Italian intelligence.
Alessia Sorgato and Guido Meroni, lawyers who represent some of the Americans charged, have argued that the evidence connecting their clients to Nasr's disappearance was circumstantial, based on phone records and their presence in locations in Italy during the period before the abduction.
During the proceedings, an Italian police officer and another suspect struck plea bargains. Two other Italian intelligence agents also were indicted on lesser charges, as accessories.