A major land and air search is under way for a group of five hillwalkers who have not been seen since Wednesday.
Police said around 30 people are searching the Loch Muick area of the Cairngorms.
Police said the weather in the area was "atrocious" yesterday, with winds reaching speeds of 165mph in Scotland.
The alarm was raised last night when five men did not return from their hike.
Police said the men, aged between 29 and 40 and all from Aberdeen, left at lunchtime on Wednesday.
Inspector Andrew Todd, who co-ordinates mountain rescue operations in Grampian, said: "The men were expected to return on Thursday evening and, although we believe the men were all well-equipped and experienced walkers, given the atrocious weather conditions in the area yesterday we have a serious level of concern for their well-being.
"We searched areas during the night and we have now deployed a full-scale mountain rescue team which involves around 30 people at present. The search is focused on the area to the south of Loch Muick and Glen Clova.
"At present the search involves the joint Grampian Police and Braemar mountain rescue team, as well as Tayside Police and volunteer mountain rescue.
"The search is also being supported by a Royal Navy search-and-rescue helicopter and three dogs from the Search and Rescue Dogs Association."