There will be significant point increases in this year's CAO system, the chairperson of the Central Applications Office Board has said.
Professor Pól Ó Dochartaigh said there will be added upward pressure on points when compared to last year, mainly due to an extra 6,000 applications which are expected.
Speaking on RTÉ's Today with Claire Byrne, he said which courses the 6,000 extra applications will be relevant to will be clear by the beginning of March.
He said grade inflation put upward pressure on points last year.
Prof Ó Dochartaigh, who is also Deputy President NUI Galway, said the extra expected applications are a result of four factors.
"The first thing is that there are 2,000 more students doing the Leaving Cert in Ireland this year compared to last year," he said.
"The second thing is with Brexit having happened, the UK jurisdictions are no longer required to treat Irish students in the way they would treat UK students, so Irish students will have to pay more to study there."
"The third thing is that in any economic downturn, there is usually an increase in the number of mature students who decide now is the time to get that qualification that they should have got when they were younger.
"The fourth unknown factor is again going back to Brexit. We don't know what kind of numbers of students in the past from other EU countries have decided they wanted to study through the medium of English, so they went to the UK.
"That will now cost them a fortune. So how many of them will look at Ireland?"
Prof Ó Dochartaigh said there will not be capacity to provide the required number of placements for "higher points courses" like medicine, and said it would not be fair to offer the course, if the clinical placement cannot be guaranteed.
"We have to be realistic about our reaction, in terms of what the expectations are and what the capacity is to deliver on. If we react like we did last year, on an awful lot of the courses, particularly high demand courses, it will not work."
Prof Ó Dochartaigh said it will be difficult to guarantee that a parallel running of a traditional Leaving Cert and a calculated grade system are providing "comparable" results.
Meanwhile, Taoiseach Micheál Martin has said there will be clarity on this year's Leaving Cert next week.
