A woman mugged a pensioner in Portslade, stealing the necklace that her victim was wearing.
The robbery happened near the bus stop in Trafalgar Road close to the junction with Victoria Road.
The thief approached the elderly woman, took the necklace from around her neck and made her way round the corner into Victoria Road.
There she was believed to have got into a black car and driven off.
Sussex Police said that the robbery took place at about 6.10pm last Monday (1 August).
A spokesman urged any witnesses or anyone with information to contact Sussex Police on 0845 6070999 or the independent charity Crimestoppers anonymously on 0800 555111.