The hearings have been lambasted by foreign governments, lawyers and human rights groups.
The men face varying charges of conspiracy to commit terrorism. None are accused of killing Americans.
While the maximum sentence they face is life in prison, the military commissions - the first in nearly 60 years since the United States tried German saboteurs - will have the power to sentence others to death and there is no independent appeal process.
Significant challenges already exist before the first scheduled hearing.
One defence attorney has not seen his client in four months because of a government delay in giving clearance to a translator.
Another defence lawyer has withdrawn from the case after accepting another job, leaving her client with no representation.
Others say the broad restrictions, which include the military's right to monitor conversations between attorneys and clients, will make it almost impossible to win their cases.
The Bush administration has
defended the process
Jumana Musa, a representative of Amnesty International, said the system was unfair because it was so tilted towards the prosecution and there was no independent body involved in the appeals process.
"I don't think it is a concern that because they are drawn from the military per se that they can't be independent. The concern is that there is no independent body that anyone can appeal to."
Musa added: "The concern here is that the whole process itself is entirely closed where if they appeal they don't appeal to an appeals court outside the system, they just appeal up the chain of command within the same system."
But the Bush administration has defended the process.
One issue the commission authorities expect to come up involves the use of information against the men that could have come from interrogations at Guantanamo and other overseas outposts.
Several detainees released from Guantanamo Bay claim to have made false confessions during interrogations lasting anywhere from two to 15 hours.
Detainees were subjected to
arduous interrogation sessions
Only four of the Guantanamo detainees have been charged so far, while charges against 11 others are pending approval. Most of the men in the camp have been refused access to attorneys.
All are considered enemy combatants - a classification that, unlike prisoners of war, allots the men less protection under the Geneva Conventions. Military commissions are reserved for foreign-born captives and have lower standards for prosecution than American civilian courts.
At this week's open preliminary hearings - expected to last four days - charges will be read to the men, who can enter pleas. Their lawyers will also be able to make motions.
It could be months before the military commissions or trials begin.