Up to 30,000 people travelled to Croagh Patrick in Co Mayo today for the annual pilgrimage.
Pilgrims began climbing the 764-metre high mountain from early this morning.
Mayo Mountain Rescue appealed to people to take care on their ascent and descent.
The organisation said anyone planning on walking in bare feet should bring shoes as a back up.
Flip-flops, wellingtons, sandals or stilettos are not recommended.
So far, the organisation has attended to 17 casualties. Four people had to be taken off the mountain via stretcher, and two helicopter evacuations also had to be organised.
Most of the injuries were broken bones and sprains. One person suffered a head injury.
In a homily during mass on Croagh Patrick this morning, the Catholic Archbishop of Tuam, Michael Neary, said the church should be a "counter-movement" to today's society.
He said recent economic and social upheaval had led to a questioning of value systems.
But he said an urge for political correctness meant society was attempting to make sense of the world without reference to God.
Dr Neary said he feared that Christian beliefs were no longer given the same respect as that accorded to the "faith of Israel" or "the convictions of Islam".
He said that all religious traditions had to be valued if there were to be proper understanding and tolerance of different cultures.
Croagh Patrick has over 100,000 visitors annually.