A 17-year-old boy was robbed of his mobile phone at knifepoint.
Two men approached him at Sherborne Road, in Chichester, close to the junction with Westgate.
One punched the boy in the face and a knife was held to his throat.
The robbery happened at about 2am last Saturday. One suspect was described as white, aged in his mid to late-20s, 5ft 11in, of medium build with short brown hair. The other was aged about 29, 6ft 5in, and wore a long-sleeved grey hooded top and tracksuit trousers.
Both spoke with Eastern European accents. Call police on 0845 60 70 999.