During the shoot, many of the crew members got rashes from bed bugs in their hotel rooms.
According to Lynn Collins, director William Friedkin never took more than four takes to get a scene in this film, and in fact worked so fast that the actors sometimes had to beg him to do a second take when he thought they'd nailed it the first time.
The film was shot in July and August of 2005 in Southern Louisiana, and wrapped up only a week before Hurricane Katrina hit the area; the cast and crew narrowly escaped the disaster by only a few days.
The entire script was shot in chronological order.