The event was heavily policed
Fears multinational companies would be the target of violence during May Day demonstrations in central London have proved groundless.
Some businesses told staff to stay at home, while others stepped up security ahead of the march.
Oil and arms companies, firms with connections to Iraq and government buildings were thought to be possible targets for anti-capitalist protesters.
In past years marches have become violent with the more extreme demonstrators smashing windows and forcing their way into buildings.
But this year's event, which went under the banner "Mayday 2003 Weapons of Mass Construction - Our Day", passed off relatively peacefully.
Around 300 demonstrators gathered outside the offices of US defence contractor Lockheed Martin, in High Holborn.
The protest is being conducted in a peaceful and orderly fashion
Some protesters unfurled flags and staged a sit-down protest in the middle of the road.
Scuffles broke out as police tried to move the protesters along.
Officers stopped the traffic and swamped the area.
The offices of the multinational company were boarded up and cordoned off, preventing protesters from getting close to the building.
Lockheed Martin had told its staff to work from home rather than run the gauntlet of demonstrators.
The oil giant Shell, which was chosen as the end point for Thursday's march, said it had its business had not been disrupted by the protests.
Shell spokeswoman Bianca Ruakere said "about 20 or 30" demonstrators had gathered outside Shell's building on the South Bank.
She said the demonstrators shouted slogans through megaphones.
But the demonstration had been "conducted in a peaceful and orderly fashion".
Lockheed Martin, Shell and all the other companies indentified as potential targets along the route, have been advised by the Metropolitan Police.
The businesses thought to be most at risk were briefed at New Scotland Yard and visited by officers.