He was driving a Mazda 5 when it and a white Audi A3 collided at a junction on Shoulderigg Road near Coalburn in Lanarkshire.
Following the crash, at about 16:30 on Friday, he was taken to the Queen Elizabeth University Hospital in Glasgow.
He is suffering from multiple injuries, including a serious head injury.
The man's passenger, a 10-year-old boy, was released from Wishaw Hospital after treatment for minor injuries.
The 22-year-old man who was driving the Audi remains in Wishaw Hospital, where his condition is described as stable.
Sgt David Stenhouse said: "Although this is a rural road, there were motorists and others in the area at time of the crash.
"I would appeal to anyone who has not yet come forward to speak to the police about what they saw, to do so as it would assist the investigation."
A 61-year-old man remains in a critical condition in hospital after a two-car crash.