The world record for time without sleep is 264 hours (11 days) by Randy Gardner in 1965.
John J. Ross, who monitored his health, reported serious cognitive and behavioral changes. These included moodiness, problems with concentration and short term memory, paranoia, and hallucinations. On the fourth day he had a delusion that he was Paul Lowe winning the Rose Bowl, and that a street sign was a person. On the eleventh day, when he was asked to subtract seven repeatedly, starting with 100, he stopped at 65. When asked why he had stopped, he replied that he had forgotten what he was doing.
On his final day, Gardner presided over a press conference where he spoke without slurring or stumbling his words and in general appeared to be in excellent health. "I wanted to prove that bad things didn't happen if you went without sleep."
After completing his record, Gardner slept 14 hours and 40 minutes, woke naturally, stayed awake 24 hours, then slept a normal eight hours. Makes me tired just thinking about it.