The course which started on Tuesday includes the handling of classified information which came in response to the indictment of a top aide in the CIA leak investigation.
Bush's top political adviser, Karl Rove, was expected to attend one of the classes scheduled for Wednesday.
A total of 3000 administration officials - with the exception of Bush and Vice-President Dick Cheney - will attend the mandatory, one hour-long briefings over the next two weeks, White House spokesman Scott McClellan said.
Cheney's new chief of staff, David Addington, was also scheduled to attend, the White House said.
Held in an auditorium next to the White House, the briefings are being led by Richard Painter of the White House counsel's office and cover rules for safeguarding national security secrets.
Lewis 'Scooter' Libby has been
indicted in a CIA leak case
The ethics course comes after Cheney's former chief of staff, Lewis "Scooter" Libby, was indicted on five counts of obstructing justice, perjury and lying in the two-year investigation into the leak of covert CIA operative Valerie Plame's identity after her husband criticised the Iraq war.
Plame's identity was leaked to the media in July 2003 after her diplomat husband, Joseph Wilson, accused the Bush administration of twisting intelligence on weapons of mass destruction to justify the war in Iraq.
If convicted, Libby, who resigned from his post in the White House, faces a maximum sentence of 30 years in prison. He has pleaded not guilty.
Democrats sought assurances from Bush on Tuesday that he would not pardon Libby or any other officials found guilty of crimes stemming from the Plame investigation.
"The president thought it was important to have these refresher briefings for all White House staff in light of recent circumstances. It is mandatory"
White House spokesman
McClellan would not comment on the prospects of a presidential pardon for Libby or anybody else. "I'm not going to discuss an ongoing legal proceeding. And I'm not going to speculate about any matters relating to it," McClellan said.
The five-count indictment against Libby maintains that other government officials were aware of, if not involved in, leaking the identity of Plame to the media. One of those officials is Rove, who serves as Bush's deputy chief of staff.
Rove was not indicted along with Libby, but lawyers involved in the case said Rove remained under investigation and may still be charged in the case.
The briefings were scheduled for staffers according to the first letter of their last name. If that practice is followed, Rove would be expected at a session at 4pm on Wednesday.
"The president thought it was important to have these refresher briefings for all White House staff in light of recent circumstances," McClellan said. "It is mandatory."
The White House counsel's office will conduct eight presentations on Tuesday, Wednesday and Thursday for those aides with security clearances.
Briefings for all other aides in the White House and the executive office of the president will take place next week.
Bush aide Karl Rove is under
investigation in the CIA leak case
Topics include the proper handling of classified national security information, who is allowed to see it, and how to dispose and transport it.
The ethics briefings come amid pressure from congressional Democrats to fire Rove or strip his security clearance.
Asked if Rove still had his security clearance, McClellan said: "Yes."
"Karl Rove is continuing to perform his duties as deputy chief of staff and senior adviser. We appreciate all that he's doing," McClellan said.