Wiltshire Police is appealing for any witnesses to the incident, which occurred at 4.30pm, when a Hyundai Sirion travelling eastbound and BMW Coupe travelling westbound collided.
The 80-year-old man driving the Hyundai and his female passenger were taken to Great Western Hospital with serious injuries, but were in a stable condition as of 10pm last night.
The 54-year-old man driving the BMW was not reported having suffered any injuries.
Covingham Drive was closed for two-and-a-half hours after the incident, whilst police investigated the scene and aimed to establish the cause of the collision.
A spokeswoman for South West Ambulance Service said: "We were called at 4.20pm to a two-vehicle head-on collision where two elderly patients were reported.
"Both patients were taken to GWH and one had suffered what were described as potentially life threatening injuries. They were taken straight into resus.
"A paramedic initially arrived on the scene in a rapid response vehicle within a couple of minutes, before two full ambulances were called."
Any witnesses, who have not already spoken with police, should contact PC 1310 Cooper at Wiltshire Police, using the non-emergency 101 contact number.