When the film was first screened in Hong Kong, a stunned silence followed it for a few seconds that was followed by complete uproar. Bruce Lee was mobbed as he tried to leave the theatre.
Bruce Lee sprained his ankle badly while landing awkwardly from a jump. He couldn't move properly and was also racked with aches and fever and was having difficulty keeping food down. Even so, filming continued. His twisted ankle meant that he had to drag his injured leg, so in several scenes he had to be filmed in closeup. He also broke a glass in his hand, resulting in a gash that required ten stitches. While at the hospital in Bangkok, he caught flu and rapidly lost ten pounds.
The Thai brothel featured in the film was actually a genuine and functioning brothel. The extras who feature in these scenes (excluding Malalene's character) were actual prostitutes who were paid more by Golden Harvest than they would normally receive in a day by their clients so that they could appear in the film.
In the first week of filming, Bruce Lee was increasingly annoyed by the haphazard production. The equipment used for filming was old and in bad repair and the script consisted of a few basic ideas scribbled on scraps of paper.
In 1971, this was the highest grossing film of all time in Hong Kong, beating out American productions The Sound of Music (1965) and Tora! Tora! Tora! (1970).