Bruce Lee cast Chuck Norris in the film, because he was one of the few who was fast enough to take him on. Chuck asked Bruce if he wanted to fight the champion (at the time, he was the US Karate champion). Bruce replied, "No, I wanna kill the champion".
According to the assistant director, Ching-Shun Mao, filming around the Colosseum was strictly forbidden, and the few scenes actually filmed there were quickly shot without the knowledge of the Roman authorities.
In the Chinese language versions of the film (Cantonese and Mandarin), Korean actor Wong In-Sik actually spoke both English ("Who can do Karate better than the Japanese?") and Japanese ("Omae wa Tang Long ka?" meaning "Are you Tang Long?).
Unlike The Big Boss (1971) and The Chinese Connection (1972), in which guns only come into play when cops appear in the endings, the film has a more consistent presence of guns throughout the film. Even Tang Lung asks if he can buy a gun. This most likely comes back to an answer Bruce Lee gave in "The Lost Interview", when he was asked why so many martial arts films were period pieces. He simply used his fingers to mock pulling a gun out of his jacket, saying that this was the big reason. This would also come into play in_ Enter the Dragon (1973)_, when he asks "why doesn't somebody pull out a .45 and *bang*, settle it?" in regards to taking out the main villain, Han.
Most of the crew did not have international passports or working visas which meant they could only work in Rome for a maximum of three weeks. Bruce Lee and the crew made sure they got all of their required footage within just two.
In a phone interview with journalist Alex Ben Block during a lunch break on the set during early production, Bruce Lee confirms that the original working title for was originally 'Enter the Dragon'. However, once Bruce had gotten wind, that Hollywood had become interested in making a martial arts film with Bruce as the lead role based on the success of his two earlier films made in Hong Kong, Bruce decided to reserve the name and title 'Enter' for his first Hollywood breakout film and changed the name of this film to 'Way of the Dragon'.
Bruce Lee made several 'firsts' in the Hong Kong movie industry whilst making this. It was the first Chinese film be made in the West, and he was the first Hong Kong director to view daily 'rushes' in color. He insisted on doing this so he could ensure exact color - matching in editing, due to combining the location shots in Rome with the studio footage at Golden Harvest. He also refused to use the standard 'canned' music and commissioned a new score.
The trivia items below may give away important plot points.
This is one of only two films in which Chuck Norris plays a villain (the other film, Huang mian lao hu (1974), AKA: "Yellow Faced Tiger", is also a Hong Kong-produced film), and the only film in which he is killed (he is only knocked out in the other film as the villain).
In the final fight between Tang Lung and Colt, Tang is using the traditional Kung Fu approach but nearly loses the fight. However when Tang begins to use the approach of Jeet Kune Do Tang gets the upper hand.
Part of the music in this film is actually originally from the Ennio Morricone score for the Sergio Leone western Once Upon a Time in the West (1968). The music used for Chuck Norris is taken from that film's track, "As A Judgment" (AKA: "The Grand Massacre"), and "The Transgression" was used in many of the suspenseful scenes (including when Bruce Lee explores the Colosseum to face Chuck Norris' character). Additionally, an excerpt of a track from John Barry's score for the James Bond film Diamonds Are Forever (1971), "Death At The Whyte House," was used in the scene where Uncle Wang, showing his true colors, wickedly stabs Tony and Jimmy in their backs with a knife.