A record-breaking number of A-level entries for England, Wales and Northern Ireland have been awarded A grades.
More than one in four entries - 26.7% - got the top grade, up from 25.9% last year and the overall pass rate rose to 97.5%, up 0.3 percentage points.
The improvement in grades - for the 27th year in a row - will add to the pressure on university places.
There are 60,000 more applicants for university places in the UK than this time last year.
That is a 10% rise on last year. The increase is being put down to demographics - more people in that age group this year - and the effects of the recession.
Hundreds of thousands of teenagers have received the results of their A and AS-level exams.
Scottish students received the results of their Highers and Standard Grade exams earlier this month. They showed a slight rise in standards achieved.
The A-level results have been released by the Joint Council for Qualifications (JCQ), the body which represents the exam boards.
They show that more than three quarters of entries (75.1%) were awarded at least a C grade.
In Northern Ireland, more than one in three entries (34.5%) was given an A grade - a fall on last year when 35.4% achieved the top grade - but still a higher proportion than in England and Wales.
In Wales, 25% of entries got the top grade. In England, the proportion was 26.5%.
The figures reveal that girls continue to outshine boys generally at A-level, but that the gap between them at the top grade is narrowing.
The percentage of entries from boys which were awarded an A is 25.6% this year, compared with 27.6% of entries from girls.
The results show traditional subjects remain the most popular at A-level, with English and maths the top choices.
There were an extra 7,882 entries for maths this year, and an extra 1,382 entries for further maths.
There was also an increase in the number of entries for chemistry and physics, but a fall in the number taking biology.
Fewer people took French and German this year. There were 552 fewer entries for A-level French - a fall of 3.7% - and a 7.7% drop in those taking German.
Jim Sinclair, director of the Joint Council for Qualifications (JCQ), said: "These are excellent results. They are the outcome of hard work of students and teachers, who deserve to be congratulated.
"It is particularly good to report improved uptake and outcomes for mathematics and science."
Figures presented by the JCQ at a media briefing show the proportion of top A-level grades awarded to independent schools is increasing.
About 50% of entries from the independent sector were given A grades, the exam boards said.
This compared with about 40% of entries from selective state schools and about 22% of those from other state schools.
Clearing pressure
In response to the surge in applications to UK universities, the Westminster government recently announced partial funding for 10,000 extra places in "priority" subjects - predominantly sciences, engineering, technology and maths.
There have been rises in numbers applying to most of these subjects, with the exception of chemistry.
Those who do not achieve the grades needed for their degree offers can use the "clearing" system to search for an alternative available university place, but the pressure on places means fewer students will find a course this way this year.
It is thought about 22,000 places are available available by this route - about half the number allocated through clearing last year.
The university admissions service Ucas has said 135,114 students are already eligible. At this time last year about 109,000 people were eligible for clearing.
That suggests there are roughly six applicants for every place available through clearing, so many will be disappointed.
Oxford and Cambridge saw record applications for the next academic year - around 15,000 people applied for the 3,000 or so places on offer at each institution.
Dr Wendy Piatt, Director General of the Russell Group of research intensive universities, told the Today programme on BBC Radio Four universities were facing pressure for places.
"We are turning away candidates with not just three As but four As," she said.
However, she added, universities strove to look at the whole candidate, not just their grades, and A-levels, although not perfect, were "on the whole, fit for purpose".
Diana Warwick, chief executive of Universities UK, said: "Although it's not new to see intense competition for places during clearing, we know things will be tighter over the coming days due to the large number of applicants for university places this year.
"All those who achieve the grades asked for in their offers will be guaranteed places, as always, and we congratulate this year's A-level candidates on the successful outcome of all their hard work.
"Universities are experienced in handling high numbers of applications and they have been preparing for this peak time for many months now, along with Ucas."
The Conservatives said ministers were to blame for the thousands of students who may miss out on a university place.
Shadow education spokesman David Willetts said: "I congratulate all those who have received their A-level results. Their success reflects an enormous amount of hard work.
"It is tragic that ministers are now blocking the path to university for so many of them.
"The government first reduced the number of university places, then offered only unfunded places and are now threatening to fine universities that over-recruit. They said they wanted half of all young people to go to university by 2010, but now they are blocking progress towards their own target."
Liberal Democrat spokesperson for universities, Stephen Williams, said students applying to study arts subjects would not benefit from the extra places announced.
"The irony is that while a record number of students are likely to get the top grades, more young people than ever are going to be disappointed as they fail to get a place at university."
Schools Minister Iain Wright said the government had expanded university education.
"This September will see more young people than ever before starting higher education. This is a transformation in education participation and attainment which should be a cause for celebration not criticism."
"The entrance into university is always a competitive process. We've provided more resources, we've provided more money, which contrasts to the Conservatives point of view, which wouldn't provide a single additional place for university students.
"There are 10,000 additional places in addition to the massive investment in higher education that we've provided over the last decade. I would say to students, don't give up hope, there is options available there."
(www.eduwo.com, Jainlyn&Charlotte)