Rescuers are searching the Wicklow mountains near Blessington for a 71-year-old man reported missing two days ago.
Walter Hammond of New Haven, Blessington, was reported missing on Thursday when he failed to return from a hill-walking trip.
A search of his proposed route by mountain rescuers failed to find him.
Mr Hammond is described as 6 feet 3 inches tall and well built. When last seen he was wearing a navy anorak, navy fleece and he was carrying a black and wine rucksack.
Gardaí have asked that any members of the public, particularly any hill walkers who may have been walking in the Mullaghcleevaun or Black Hill area and who may have seen a man fitting Mr Hammond's description, to call them at Baltinglass Garda station on 059-6482610.
Gardaí, Civil Defence personnel and local mountain rescue volunteers are involved in the operation.