Al Pacino had difficulty with his scenes with Jorge Porcel The actor, who made 50 films in Argentina, spoke no English, and learned his lines phonetically.
Al Pacino and Penelope Ann Miller became romantically involved during filming. Miller spoke publicly about their romance in interviews. But Pacino was in a relationship with Lyndall Hobbs at the time. Pacino attended the film's premiere with Hobbs and avoided Miller entirely.
John Leguizamo turned down the part of Benny Blanco four times. He finally took the role after Brian De Palma allowed Leguizamo to improvise many of his lines.
According to writer David Koepp, Al Pacino and Sean Penn had trouble with the hospital scene, so Koepp kept rewriting it to the point of being requested on set by Brian De Palma when the scene was shot. Before shooting, Pacino wasn't really convinced with it because he sensed his character would never go to the hospital. They eventually shot it anyway.