Police are seeking witnesses to a crash on the Jevington Road, between Polegate and Friston, which sadly proved fatal to one of the passengers involved.
It happened at around 2.15pm on Sunday 8 May when a grey Renault Scenic travelling south was in collision with a beige Nissan Qashqai heading north near Butchershole Bottom, Jevington.
A white Vauxhall Mokka travelling south was also involved but undamaged. The road was closed for more than four hours.
An 89-year-old woman from London, who was a rear seat passenger in the Renault, sustained serious injuries and died five days later at the Royal Sussex County Hospital, Brighton.
Several other people were slightly injured and were either treated in hospital or at the scene before being allowed home.
Roads policing officer Sergeant Clare Kenward said: "We're keen to hear from any witnesses to the crash or from other drivers who may have seen the vehicles involved being driven prior to it happening."
They are asked to email any information to email@example.com or phone 101, quoting Operation Caterham.
A 62-year-old man and a 26-year-old man, both from London, were arrested at the scene on suspicion of causing serious injury by dangerous driving. Both have been bailed until 24 June while enquiries continue.