A man was stabbed in Crawley on Friday afternoon (October 4).
Emergency services were sent to the incident near the Southgate roundabout just before 3.30pm.
The 25-year-old victim, from Horley, suffered several stab wounds to the body, police said, and was taken to Brighton hospital where he is in a serious but stable condition.
Sussex Police said a member of the public called an ambulance after finding the victim, who is being treated for six stab wounds to his abdomen, arm and leg.
The man was initially treated by police officers on the verge near the Cheals roundabout in Southgate before the ambulance arrived.
Detective Sergeant Joel Brookes, of Crawley Investigations, said: “We are in the early stages of our investigation and are pursuing a number of lines of enquiry to trace the person or people responsible for this assault.
“It is possible the victim may have been assaulted close to where he was found and we are appealing for any witnesses or anyone with information to come forward.”
Anyone able to help is asked to contact police online or by calling 101, quoting Operation Edgbaston.
Alternatively they can contact the independent charity Crimestoppers anonymously on 0800 555111.