Two men were robbed as they walked to a nightclub in Dewsbury town centre.
The men, aged 19 and 20, were walking along South Street at the junction with Daisy Hill when a silver taxi pulled up alongside them.
One of the passengers in the taxi asked the victims for a lighter while ushering them over to a dark area near the taxi rank at around 11.30pm on April 26.
The second suspect then threatened them with a knife while the other began to search them.
The men then ran away with a mobile phone, cigarettes, cash and a wallet.
The first suspect was described as white, in his mid-20s, around 5ft 10ins tall, stocky, wearing a dark hooded top and speaking with a local accent.
The second suspect was also described as white, in his late teens, 5ft 11ins tall and skinny. He was wearing a black gortex jacket.
Police would like to speak to witnesses or the taxi driver who carried the two men believed to be involved.
Call police on 101.