A cyclist was found unconscious on the side of a road in Royal Wootton Bassett on Friday.
Emergency services received a call to the scene in Blacklands Road, Flaxlands, just after 4pm following reports that a man had been found unconscious and not breathing.
He is believed to be in his 40s.
A paramedic in a rapid-response vehicle was sent to the scene. An ambulance and the Wiltshire Air Ambulance followed, as well as four police cars.
The cyclist received life support and is believed to have suffered a heart attack.
Drivers were advised to avoid the area as the road was closed while the cyclist was treated.