The scene on the street where Lt. Colonel Slade falls over a garbage can was actually unplanned.
Al Pacino would often remain in character off set, using his cane to walk with and never looking at anyone when they talked to him.
Al Pacino was helped by a school for the blind in his preparation for this role. He said that he made himself appear blind by not allowing his eyes to focus on anything.
Al Pacino originally turned down the lead, and Jack Nicholson, Harrison Ford, Dustin Hoffman and Joe Pesci were considered. On his agent's advice Pacino reluctantly accepted the part. He later gave his agent credit on Inside the Actors Studio (1994) for making him reconsider taking his Oscar-winning role.