The event, which takes place on 28 October 2012 at the Old Vic, is the forerunner to the annual 24 Hour Celebrity Gala, which this year is based around musicals and takes place on 9 December.
For the first time this year, the age limit for 24 Hour Plays was increased from 25 to 30.
The 2012 participants are:
Steve Winter, director of Old Vic New Voices, said: "With over 2,000 applicants we have been spoilt for choice this year and seeing all of the 1,800 actors that applied was not only a joy but also demonstrates our commitment to finding the very best talent possible.
"What was particularly heartening was to see so many applicants from the upper age limit of 30 years, be it writer, producer, director or performer proving that ‘new voices’ are not just teenagers but a mixture of people all eager to fulfill their creative potential."