Continuity mistake: After the final explosion the camera shows a closeup of the car keys in the ignition, a Ford. Camera shows him driving away in a Cadillac.
Continuity mistake: Kris Kristofferson goes to Porter's apartment to find his son. When the phone starts ringing it is right on the edge of the table, right behind the ashtray. However, when the scene gets to where he bends down to answer the phone, the phone is in the middle of the table NEXT to the ashtray. (01:31:10)
Continuity mistake: In the scene where Val Resnick is looking at buttons of the doorphone we can see that there are only four rooms (from 401 to 404) on the floor where Rosie lives. But the room which is opposite Rosie's room is 407. You can see it when Val comes in Rosie's room with a gun. (00:51:57)
Continuity mistake: In the scene where Val Resnick points to the button of the door phone, which Porter stained with blood, we can see that it is number 403. But actually Rosie lives in room number 404. You can see it earlier, when Rosie opened the door to her apartment in order to meet Porter. (00:51:59)
Continuity mistake: When Porter leaves the apartment of the prostitute, and returns busting through the doorway only to find Val beating up the girl, he then shoots Val in the shoulder. As the shots switch back and forth, from Porter and the others, the door he just came through is open wide in some scenes, and almost shut in others. (00:56:40)
Continuity mistake: When Porter goes to see Carter in his office to get his money, porter throws a roll of coins at Carter that he used to punch out the two body guards. Carter takes the roll and rolls it on his desk towards Porter. The very next couple scenes, the roll of coins is missing from the desk. (01:06:20)
Continuity mistake: When Porter, Val and Lynn make the 'hit' on the Chows in the beginning of the movie, their car changes from a 1970 Nova to a 1973 Nova. It is apparent by the differences in the grill: There are square, orange parking lights in the grill on a '73 and there are no parking lights in the grill of a '70.