Revealing mistake: When Ash shoots Cheryl through the door in the head, you can clearly see the hose (not an artery) that's squirting out the blood.
Continuity mistake: When Scotty honks, and the two guys on the side of the street wave their arms, the window of the car is suddenly open (it was closed before, as can be seen by the reflection) and then again is suddenly closed.
Visible crew/equipment: When the people are driving over the bridge at the start, it goes to a shot of the front of the car. To the right of the car you can see a crew member holding a still camera.
Continuity mistake: The actors' haircuts change a few times. This is noticeable when Scotty pulls back the bath curtain, and his hair is rather long and thick, but when he turns around, his hair is much shorter. Also, Linda's hair is short and wavy, but when she turns evil and she and Ash are fighting outside, her hair is very curly.
Continuity mistake: When Cheryl is running through the woods, she is wearing slippers that stay on up until she reaches the cabin door. However, in following shots, she is shown barefoot, and when Ash opens the door her foot is dirty as if she'd been running barefoot the whole time.
Audio problem: When their car is making a sharp turn at the beginning of the film, you can hear the tires screeching. This could only happen if they were on concrete, not on a dirt road.
Continuity mistake: The clock in living room of the cabin shows 5:52p (approx.) at the time it stops toward the beginning of the film. At the point that Scott is "re-animated" and attacks Ash in the climactic scene, it shows 3:10 until it restarts at the very end. This change is NOT accounted for by the clock running backwards as Ash is coming up from the cellar with the shotgun shells as the next shot of the clock shows it to again be at 5:52.
Continuity mistake: After the recently possessed Cheryl stabs Linda in the ankle with a pencil, she draws back her arm to attack again and her wrist is grabbed by Ash to prevent her from doing so. The shot of the stabbing shows the pencil to be covered with blood,but in the close-up of her being stopped by Ash, no blood on the pencil. The pencil is bloody again in the shot of Cheryl coming after Ash after having tossed him and Linda aside.