The back ground music/tune in Dharmatma during the exact moment in the scene where Feroz Khan holds Rekha's hand on the bed was used in a song in Nastik. The music/ tune at 0:33 - 0:39 of the song "Aaj Ka Yeh Din", was very similar to the bgm when Feroz meets Rekha and hold's her hand on his bed. The same music/tune can be heard at 1:05 in the song "Dil To Hain Dil" from Muqaddar Ka Sikandar.
Reena Roy and Kim were signed for the film. They were later replaced by Hema Malini and Sarika.
'Nalini Jaywant (I)' made a comeback into films with this movie.
The film was delayed for several years due to production problems. Once Amitabh was giving a interview on the sets of Nastik. The interviewer knew of Amitabh's ongoing frustration with the delay of the film. When the interviewer asked Amitabh when the film would be completed, Amitabh pointed to son Abhishek (who was visiting his dad) and made the statement that Abhishek could complete the film for him.
Nalini Jaywent acted in the I.S.Joher directed film Nastik released in 1953 in which she was the heroine and acted also in Nastik released in 1983 in which she played Amitabh Bachchan"s mother.