Former sex aid seller Caroline, and yoga enthusiast Sada will now have to wait until Friday evening to find out which one has been kicked out by the viewing public.
All 10 housemates voted on Tuesday for who they wanted to be first to leave, just over a week after they first entered their purpose-built temporary home at a studio in London's East End.
Although the votes were "private" as far as the other contestants were concerned, viewers were let in on the secret.
Those watching Tuesday's Big Brother update on Channel 4 could see the inhabitants of the house splitting on gender lines.
The men, almost to a man, voted to bin Sada and Caroline. The women were less united but most plumped for Darren and Andy.
But in the end it was Sada and Caroline who had proved least popular and after the programme the phone lines were opened to the public, who will now choose which one is to be the first to be evicted.
Reasons given for the eviction of Caroline, 37, from Birmingham, were her "annoying laugh" and her odd sense of humour, while London-based writer Sada, 27, was accused of being selfish and a poor team player.
They will learn of their fate shortly before one of them is asked to leave on Friday.
Revealing exploits
Big Brother watchers who tuned into the show's 24-hour internet feed on Tuesday afternoon will have seen both Sada and Caroline burst into tears on hearing of their nominations.
After being comforted by the other housemates, Caroline, who last week became the first contestant to climb into bed with another, Liverpudlian builder Craig, said: "It's completely cool. I'm happy about it and I don't want anything to change at all."
But Sada, who spent last weekend trying to persuade the other women to vote to evict a man, said she was so upset she is now considering leaving the house of her own accord.
The eviction vote revealed a clear dividing line between the male and female camps in the household.
Everyone save psychology graduate Mel, 26, from London, who opted for a man and a woman, used both their votes to nominate members of the opposite sex.
Tension has been mounting in the Big Brother houshold since the TV show's launch.
Following a good-humoured tell-all secrets game and semi-nude pottery-making session, the housemates settled into strict male and female cliques.
Bookies' favourite
Bookmakers Ladbrokes issued new odds for the most likely person to scoop the show's £70,000 prize money in the light of the housemates' voting results.
Mel is now 5/2 favourite to stay the course until the end, with Sada and Caroline listed joint bottom, on 25/1 each.
The results of the nation's voting will be announced in Friday's live episode of Big Brother at 2030 BST.
The evictee will then leave the house at 2300 BST and join Davina McCall, friends and family for a live studio show.