Oscar Pistorius must run the first leg if he is to take part in the 4x400m relay at the World Championships, athletics' governing body has said.
The South African will make history in Daegu, South Korea when he becomes the first amputee athlete to compete in the able-bodied worlds.
"He must run the first leg to avoid danger to other athletes," said IAAF head Lamine Diack.
Pistorius has carbon fibre prosthetic blades in place of his lower legs.
The 24-year-old will also compete in the individual 400m at the meeting, which begins on 27 August.
An IAAF ban was overturned in 2008, allowing Pistorius to compete against able-bodied athletes.