Northern Ireland's students performed the best of all, with 75.1% of exams gaining an A*-C grade and 27.1% scoring an A or A*.
In England, 66.9% of exams scored an A*- C grade and 21.5% were A or A*s. In Wales, 65.5% were A*- C and 18.9% were A or A*s. Wales' Education minister Jane Hutt said: "Our young people have every right to celebrate today. Their excellent achievements are testament to their hard work and the support of their teachers and parents."
Students in the South East of England scored the highest proportion of top grades of any area in the country, with 70% of exams scoring a C or above and a quarter of exams receiving an A or A*.
The lowest proportion of A's and A*s came from Yorkshire and Humberside, at 17.8% of all grades. The same region also had the lowest proportion of passes at C grade or above of anywhere in England, at 63%, but its overall pass rate has improved at a faster rate than that of other English regions.