Three people were airlifted to safety while taking part in the annual pilgrimage to Croagh Patrick.
An estimated 12,000 people took part in the traditional Reek Sunday trek up the 765-metre high mountain in Co Mayo.
Mayo Mountain Rescue said 19 injured casualties were stretchered off the mountain or walked to safety. An 83-year-old woman, a teenage boy and an Italian man in his 30s were also airlifted by the Air Corps helicopter.
Rescue spokesman Shane Maguire said no-one suffered life-threatening injuries.
"The morning was very cloudy and the afternoon was clear but it was very blustery," he said.
"There wasn't the usual throngs of people today, but a couple of thousand people did the climb yesterday and a lot of people climbed it last night. We could see the torches in the dark."
Croagh Patrick has more than 100,000 visitors annually, with 20,000 taking part in the national pilgrimage in recent years. It is associated with St Patrick who, in 441, spent 40 days and nights fasting on the summit and has been carried out uninterrupted for over 1,500 years.
The climb was led by Archbishop of Tuam Michael Neary and the papal nuncio to Ireland, Charles Brown.
The Defence Forces said at about 11am a pensioner was airlifted from the mountain side and brought to the Order of Malta field hospital operating at the base of the mountain.
Almost immediately after a second call was received to medivac a teenage boy who had fallen and banged his head. He was transported directly to Castlebar hospital.
At approximately 2pm an Italian man with hypothermia was airlifted from halfway up the mountain and taken to the Order of Malta field hospital operating at the base of the Mountain.
All three are being treated in hospital.