When the film started shooting in 1972, Rajesh Khanna was a super star with barely any dates to spare while Amitabh was free and had nothing but dates. Seeing the situation, Hrisihikesh Mukherjee decided to shoot most of Amitabh's solo scenes with out Rajesh Khanna. When the under production film was shown to the film distributors, they naturally felt Amitabh was the main lead of the film with Rajesh Khanna in a special appearance. They did not want to buy the film despite it being a Hrishikesh Mukherjee film. Finally one distributor told Mukherjee that his "hero" looked like a ape with that hair cut. He went on to add that he should get a hair cut so they could see if he had any ears. When Zanjeer released and was declared a block buster, that very distributor wanted Amitabh's role to be increased and demanded Amitabh be given equal prominence as Rajesh Khanna in the film's poster's
Namak Haram has been adopted from the English classic "Becket", released in early 60s. Two stalwarts of the yester era, Peter O Toole and Richard Burton acted as the two protagonists. Hrishikesh Mukherjee made the indianization of this film with time-tested convictions. Amitabh Bachhan did the Peter O Toole's role, while Rajesh Khanna did Richard Burton's character. Both gave brilliant performances and the roles amazingly fitted their images and characterstics.
Rajesh Khanna was offered the role of Vicky first. He declined it and wanted the other role instead.
This was the second and last time Amitabh and Rajesh Khanna shared screen space after Anand due to the intense rivalry between the two
After watching Amitabh Bachchan's performance in the film Rajesh Khanna said that someone has come to replace his stardom.