Continuity mistake: As Chef and Captain Willard are walking through the jungle looking for mangos Chef says," I was supposed to go to Paris" as he's walking over the roots of a huge tree. He continues talking but in the next shot he's out in the open, nowhere near the roots of that tree.
Continuity mistake: Just before Colonel Kurtz falls to the ground we catch a glimpse of him with blood running from the top of his head down the right side of his face. Several seconds later as the lies on the ground dying there are only a few small drops of blood on the right side of his face.
Continuity mistake: Dennis Hopper holds his cigarette between the first and second finger of his left hand before he gives the water to Captain Willard in the bamboo cage. In the next shot as he gives him the water the cigarette is between his thumb and first finger. Then in the shot after that it's between his first and second finger again.
Continuity mistake: At the end of this scene the shots of Chef and Miss May in the helicopter at the Medevac were done in an entirely different place. All the outside shots of the helicopter have different backgrounds (trees, mountains, tower) from what we saw when Captain Willard first walked around the Bunnies' camp.
Continuity mistake: After the 'Valkyrie' helicopter attack, there's a close shot of a soldier who shouts: 'I'm not going.' Another soldier turns back to the chopper to pull him out. Then there is a long shot of the troops at the choppers and you see the same soldier turning back to the helicopter.