John Smith, from Machrie, was reported missing from his home on the Isle of Arran on May 30 prompting searches from mountain rescue teams, the RNLI, RAF and coastguard.
The 77-year-old was last seen by a neighbour near to Machrie Golf Club around 6.10pm and was understood to have been heading in an easterly direction to meet a friend, but never arrived.
He is described as white, 5ft4, of slim build, with short grey hair, blue eyes and a fair complexion.
When last seen, he was wearing a dark jacket, dark trousers, a woolly hat and brown hiking boots.
Police say further searches will be carried out for Mr Smith next Sunday and Monday.
Chief Inspector Brian Shaw said: “Extensive enquiries and rigorous land searches have been carried out in order to trace John, however despite our efforts he is still missing.
“Our officers have been working alongside Arran Mountain Rescue, RNLI, the RAF and the Coastguard and will be carrying out further ground searches on Sunday 10 and Monday 11 December.
“We remain committed to finding John and would urge the local community, who have been very supportive, to continue to assist us by passing on any information which could help our investigation.
“Anyone with information is asked to contact officers at Lamlash/Irvine Police Station via 101.”