Final body count: 27, all killed by Sanjuro.
For the "explosion of blood" in the final duel, chocolate syrup was mixed with carbonated water and put under 30 pounds of pressure.
In the scene where Sanjuro has to kill about a dozen of Kikui's men and then smacks three of the young samurai for forcing him to kill so many, Toshirô Mifune slapped the three young actors for real. As seen in the film, the slaps both surprised the actors and knocked them backwards.
Mutsuta's wife is shown to have what appears to be blackened teeth. This was a common type of fashion, especially with Courtiers in the Imperial Court.
This movie was originally going to be a faithful adaption of a Shûgorô Yamamoto novel called Peaceful Days, and was going to be made before Yojimbo, which is about a group of nine samurai who are helped out by two ronin who are inadequate fighters and have to use there wits to trick two evil opposing sides into disposing of each other. The antagonists was changed to a corrupt government body and the tricking two opposing sides into fighting each over element was used for Yojimbo. After Yojimbo was a success Toho requested that Kurosawa produce a sequel. He changed the two weak ronin to the powerful Sanjuro character and rewrote the script to match the tone of Yojimbo. Also when this was going to be Peaceful Days, Kurosawa was only going to write it and Hiromichi Horikawa (Kurosawa's assistant director) was going to direct it and Frankie Sakai and Keiju Kobayashi were to play the two ronin.