Portuguese transsexual Nadia Almada is the bookmakers' clear favourite to win the Big Brother final on Friday.
Nadia has better victory odds than any previous Big Brother winner
Initially a 50/1 outsider, she is now 50/1 to win at Ladbrokes and 1/10 favourite to win at William Hill.
Ladbrokes spokesman Warren Lush said: "The change in her fortunes since the start of the show is remarkable."
Viewers have been voting for the winner since Friday, with the least popular of the five remaining contestants facing a surprise eviction on Wednesday.
Of the reality show's 13 contestants, Almada remains with Dan Bryan, Jason Cowan, Shell Jubin and Stuart Wilson.
Cowan and Bryan are 16/1 to win at Ladbrokes, followed by Wilson at 33/1 and Jubin at 50/1.
But Ladbrokes said: "We can't see any other housemate making a challenge, it's Nadia all the way.
"She's the hottest favourite to win we have seen in any series."
The bookmakers had 2003 winner Cameron Stout at 1/10 to win on the eve of last year's final, while Brian Dowling was 1/16 in 2002.
Previous winners of the Channel Four series have taken prize money of £70,000 but this year's fund has been progressively depleted following failure to complete certain tasks.