Two men died in the early hours of Sunday when the car they were travelling in lost control and left the road, according to police.
Two other men in the Peugeot car were treated in hospital before being arrested on suspicion of causing death by dangerous driving following the accident near Brighton, East Sussex.
All four occupants of the car were from London, according to Sussex Police.
The car was being driven southbound on the A23 when it left the road near the A273 junction at Pyecombe, a few minutes after 1am.
The two suspects were taken to the Royal Sussex County Hospital in Brighton, but were not seriously injured.
A police spokesman said: "They were arrested on suspicion of causing death by dangerous driving and remain in police custody this morning.
"The collision impacted on both carriageways and the A23 was closed in both directions at Pyecombe while rescue, recovery and collision investigation work was carried out.
"It was re-opened at 7.25am."