According to TV Guide, "In October 1972 an account written by Leonard Greenwood appeared in the Los Angeles Times. It told of a Peruvian engineer whose son had been kidnapped by a band of Indians and of the man's successful search to locate the child. Screenwriter Rospo Pallenberg saw the news item and took it to producer-director John Boorman". The result was this movie.
Powers Boothe almost drowned during the shooting of one sequence where Charley Boorman was assisting Boothe cross a river. Boorman's pleas for assistance were initially interpreted by distant crew personnel as being part of his performance.
According to director Sir John Boorman's book "Money Into Light - The Emerald Forest: A Diary" (1985), Boorman's initial choice for the part of the son Tomme was C. Thomas Howell. When Howell was unavailable, John decided to use his own son Charley Boorman for the part.
Charley Boorman broke the same toe four times during production. After the lengthy shoot, during which he had spent virtually the entire time barefoot, his party trick was to light a match on his bare feet.
The names of the indigenous South American tribes were "The Fierce People" and "The Invisible People." There is a reference to a former tribe named "The Bat People." The members of "The Invisible Tribe" refer to the dam builders as "The Termite People."