The sixth season of CBS's American version of Big Brother consisted of thirty episodes which aired from July 7 to September 20, 2005. It was again hosted by Julie Chen.

For this season, the Big Brother house had been remodelled and enlarged: a second floor was built containing a larger Head of Household room with its own private bathroom.

Twists

The rules remaining mostly the same as in previous seasons, but this season contained twists that CBS dubbed the "Summer of Secrets".
The main twist that was each houseguest had a secret partner, who they already knew in the real world, a fact that they must keep a secret. Initially, each secret pair thought that they were the only secret pair. As a reward, should both secret friends make the final two, there would have been a grand prize of $1 million instead of $500,000. The secret pairs were April and Jennifer, who were sorority sisters; Janelle and Ashlea were ex-roommates; Eric and Maggie were friends; Howie and Rachel were friends; Ivette and Beau were formerly co-workers; Michael and Kaysar were neighbours; and James and Sarah were dating.
Another twist occurred when the America's Choice Poll allowed the public to vote on which evicted houseguest would return back into the game. While Kaysar returned back into house after being evicted, he wasn't actually the first to do as Amy from Big Brother 3 had also returned to the house (but not in a public vote).

Memorable Events

• The season was known for having the most bitterly divided house in the show's history, with more animosity between the houseguests than ever before.

• The house was divided almost down the middle into two alliances. The first alliance was known as "The Friendship" to its members but as the "Nerd Herd" to its enemies. Its members were April, Jennifer, Beau, Ivette, Maggie, and Eric. They remained largely entact until the final days when Ivette finally expressed doubts at having stuck with them for so long. The other alliance in the house was the "Sovereign Six", whose members were Kaysar (the group's founder), Janelle, Rachel, Howie, James and Sarah. This alliance was not as firm in its solidarity, however, as Howie, James and Janelle had all voted to evict Kaysar, and Janelle had also voted to evict James. After James had been caught playing both sides, Howie nominated James and his partner Sarah, leading to further fall outs within the group.

• Among the most explosive moments occurred in the second week. Eric and Michael had to be physically restrained from fighting in the backyard after Eric accused Michael of threatening his family and Michael called Eric a "midget". The same day, Kaysar and Ivette came close to a physical confrontation as well after he felt she insulted his beliefs. Big Brother had to intervene over the loudspeakers and give warnings to the houseguests.

• In the season's only actual physical confrontation, during week seven Janelle and Beau had a catfight after getting drunk from cocktails provided from a food reward. The fight included scratches, pushing and poking, and after it was broken up it continued with name calling that included Janelle calling Beau a "gold-digging whore".

• In week 8, Howie went on a 48-hour rampage against April, insulting her incessantly, calling her "Busto" (insulting her breast implants), and insulting her dog and husband.

• The Sovereign Six alliance were infuriated by Jennifer when Kaysar had allowed her to win an endurance Head of Household competition after she had tearily promised to save him. A few days later, however, she nominated him for eviction and successfully organized her alliance to vote him out.