Christos, from Greensborough in Melbourne was last seen on Big Muster Drive, Dinner Plain, north east of Melbourne, about 2.45pm on Friday.
It’s understood he went for a walk to see emus reported to be in the area, but hasn’t been seen since.
“At about 6pm that night he hadn’t returned, so his wife contacted us and she was concerned something may have happened,” Inspector Paul Hargreaves said.
“He doesn’t know the area greatly but having said that he was just out walking on a local track, the Mountain Track it’s called, that’s where we believe he went.
“What we understand is Christos is quite fit for his age, he walks approximately 45 mins every day with his dog, he’s a mobile person in good health.
“We are thinking he may have come across some misadventure or something has happened to him, maybe he got disoriented, we don’t know.
“We know we have a limited window and the conditions up there can be quite perilous.
“We hope for the best we plan for the worst.”
Emergency services have been searching for the past two days, with volunteers on horseback and foot also involved.
Hargreaves said a witness told SES on Friday night they saw a man matching his description on a popular walking track.
They want to speak to this person.
Christos, who is bald and weighs about 65kg, was last seen wearing a dark long sleeve top, jeans and white crocs.
Officers are worried Christos as temperatures are currently low and it’s extremely windy. Snow is also forecast.
Local businesses are being asked to check their CCTV.