Students taking GCSE Greek will no longer be required to know the whole story of Homer's Iliad although they will need to understand some passages in the original Greek.
The list of compulsory words that must be mastered for the higher paper of GCSE Latin exams is to shrink by almost a fifth - from 550 to 450.
For Greek, the vocabulary list will be cut from 500 words to 365.
Coursework will be cut from 3,000 words to 2,000 words and oral coursework will be scrapped, the board said.
The OCR exam board, the only one offering GCSEs and AS-levels in classical languages, said the changes were aimed at encouraging more people to take Latin and Greek.
The exams watchdog, the Qualifications and Curriculum Authority, has approved the changes.
Ken Boston, QCA chief executive, said: "Too often, Latin and classical Greek are taught as 'twilight' subjects, outside the timetable, placing additional demands on teachers and students alike.
"I hope these adjustments will encourage more schools and students to take up Latin and classical Greek."
OCR said the reforms followed broad consultation with teachers and experts in England.
A spokesman for OCR said: "The aim of this is to ensure that Latin and Greek remain a vibrant part of British education across all schools."
The move is the latest attempt to increase the popularity of Latin and Greek in schools but is likely to raise concerns about the "dumbing-down" of courses.
Lack of enthusiasm among pupils for the subjects encouraged rival exam board AQA to announce last year that it was scrapping Latin and Greek GCSEs and A-levels.
The last group of pupils to sit AQA exams in Greek and Latin will do so in summer 2006.
AQA decided to scrap its courses in the subjects despite a last-minute plea from Stephen Twigg, when he was an education junior minister, to retain them.
Dr Peter Jones, spokesman for the National co-ordinating committee for classics, said the changes were fully justified.
"It will level the playing field with other exams," he said. "The problem is we have the independent schools whose pupils frequently start Latin pretty early.
"And on the other we have the - hopefully increasing - number of other schools where students may only study the subject for a year in a broom cupboard. It is difficult to reconcile the two."
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