Unlike the other Japanese horror remakes like Le Cercle : The Ring (2002), Dark Water (2005), Pulse (2006), and One Missed Call (2008), this was the only film out of all the others that actually remained in Japan instead of moving the story to America.
Before filming, the cast and crew went through a ceremony where they were blessed so that nothing bad could happen to them for filming.
Kayako's signature croak (also referred to as a death rattle), comes from the fact that her husband Takeo had snapped her neck but hadn't killed her, and she is trying to breathe through a broken windpipe. Her stumbles also come from the fact that her ankle broke as she was trying to run away from her husband. She's also covered in blood because he slashed her repeatedly with a boxcutter (the scene that implies this was cut from the film to receive a PG-13, it was restored in the Unrated Cut).
Yuya Ozeki, Takako Fuji, and Takashi Matsuyama all appeared in Ju-on: The Grudge (2002) and Ju-on: The Grudge 2 (2003), the Japanese films upon which this film was based, all reprising their roles as the doomed Saeki family.
The character of Toshio is almost always found with his cat. In real life, the boy who plays Toshio, Yuya Ozeki, was terrified of cats.