Ravikant Nagaich stated that the film did poorly because the audience expected a film with fights and stunts. It was from the makers of Farz and Jigri Dost so they wanted more than what they got. The original ending was a sad one and the audience rejected it. The makers pulled the film out of theater's and shot a new happy climax. But it was too late. The audience was just not interested anymore.
When the film was launched, it was to star Jeetendra and Vinod Khanna in the lead roles. Jeetendra opted out due to some problems with his dates. There was some rule with the film association that limited the number of films a actor could sign. Vinod Khanna opted out because he was going to get married and take a month off work. Anil Dhawan was signed for Jeetendra's role and Amitabh Bachchan was signed for Vinod Khanna's role. Anil Dhawan had recommended Amitabh for the film because Anil Dhawan was close friends with Jaya Badhuri and both had been to FTII school together.
Amitabh can be seen singing/humming the traditional song "Mehenga Rupaiya" while walking in the film. Years later he sang the song in the album "AB Baby " by Bally Sagoo in 1996.
Tanuja had first met Amitabh in 1970 at a disco tech named Blow Up. She was very impressed with Amitabh and thought he was a very handsome man. Shortly after Amitabh was signed for Pyar Ki Kahani and Tanuja could not believe Amitabh was in the film with her. The reason being was she did not know Amitabh was a actor when she met him at Blow Up.
Koi Aur Duniya Mein Tumsa Hasin Hai. from Pyar Ki Kahani.. R.D. Burman re-used the tune of this song for another Hindi film song with a lot more success almost a decade later - "Maine Poochha Chand Se" ("Abdullah", 1979).