James Douglas Thomas, 81, who goes by the name Doug or Douglas, was last seen by his wife at 10am on Wednesday when he left his home in Spofforth to get a bus to Harrogate or Wetherby.
The police helicopter, drones and search dogs and many volunteers have been looking for Mr Thomas with searches focussing in the Harrogate and Spofforth areas in North Yorkshire and Wetherby in West Yorkshire.
Officers, and Mr Thomas’ family, are extremely concerned for his welfare and are appealing for information, however insignificant it could be.
They say it could prove vital to bringing Mr Thomas safely home.
He is described as 6ft, slim, with balding grey hair and was wearing a fawn jumper and a light-blue jacket.
People are being asked to check their gardens, sheds, garages, out-buildings, churches, community centres and local shelters in case Mr Thomas has got lost or confused.
Inspector Alex Nicholson of North Yorkshire Police said: “Thank you to everyone who has provided information or is helping with the search for Mr Thomas in any way.
“We are extremely concerned for his welfare and we are doing everything in our power to locate him safe and well.
“Please, if you have any information at all, or have seen an elderly man matching Mr Thomas’ description, contact us no matter how insignificant you might think that piece of information may be."
Call North Yorkshire Police on 101. If you have an immediate sighting of him please dial 999.