A Spanish judge has charged 29 people over the Madrid train bombings of March 2004 which claimed 191 lives and left nearly 2,000 injured.
The attacks are said to have been inspired by al-Qaeda
Most of those charged are Moroccan nationals, and the indictments run to almost 1,500 pages.
The trial is expected to go ahead early next year and to last 12 months.
So far, more than 100 people have been arrested in the course of the investigations into the attacks, which have been blamed on Islamic radicals.
Judge Juan del Olmo has accused five Moroccan men - Jamal Zougam, Abdelmajid Bouchar, Youssef Belhadj, Rabei Ousman Sayed Ahmed and Hassan el Haski - of 191 murders and 1,755 attempted murders.
Jose Emilio Suarez Trashorras, a Spaniard suspected of providing the bombers with explosives, was charged with 192 murders - including the death of a policeman killed during a raid on suspected bombers after the attacks.
The others have been charged as accomplices over the 10 co-ordinated explosions on four trains during the busy morning rush hour.
Although the attack was claimed by al-Qaeda, the investigation has suggested the bombings were carried out by a local cell that was inspired by it, rather than directly ordered by the group's senior leadership.
Videotapes and internet postings by al-Qaeda leaders had urged Islamic radicals to target Spain and other countries with troops in Iraq and Afghanistan.
The attacks led to the fall of the then pro-US government in Spain, which had initially blamed the bombings on the Basque separatist group, Eta.
The complexity of the case and the large number of accused mean the trial is unlikely to get under way before next year.