About 114,000 students have begun their Leaving or Junior Certificate exams in centres across the country today.
Almost 90 subjects will be tested during the two-week marathon with teachers warning about the dangers of study stress.
As well as curricular subjects there will also be 15 languages tested at Leaving Cert for native speakers including Romanian, Polish and Latvian.
"I want to send my very best wishes to every student commencing their Leaving Certificate or Junior Certificate examinations today," Minister for Education Batt O'Keeffe said.
"I am aware that this can be a stressful time for you and your families. It is very important that you keep the exams in perspective and bear in mind that there are many opportunities for you to continue your education after the Leaving Certificate. Give it your best shot."
For the first time this year Leaving Cert students will begin with a new mix of subjects to reduce the writing burden of sitting both English papers on the first day.
Home Economics will follow the first English paper while Chemistry will come after the second paper the next day.
"I hope that students this year will settle into the exams in a calm way," Mr O'Keeffe said.
"As a result of the new timetable, most students will have a welcome half day over the first few days of the exams and students taking both exams on the first day will see the time spent in the exam hall shortened."
Almost 90 curricular subjects are being tested in 4,600 centres nationwide.
Meanwhile the Association of Secondary Teachers Ireland has urged pupils to take care over the coming weeks and warned of the dangers of stress.
President Patricia Wroe said: "Examinations are important, but they are not everything. Your aim over the coming weeks should be to look after yourself and do the best you can.
"If you feel anxious remind yourself to keep things in perspective - no examination determines your worth as a person.
"Once an exam is over, forget it. Move on. There is nothing you can do so analysing any exam once it is completed is of no benefit to you - or your friends."
In true exam-time style, Met Éireann is predicting the first few days are to be marked with some showery conditions but plenty of sunny spells.
The examinations run until June 19th for Junior Cert and June 20th for Leaving Cert subjects.
The written examinations for the Leaving Certificate Applied end on June 12th.
The results for the Leaving Cert will be available on August 13th and Junior Cert results will be out in mid-September.
PA