Revealing: In the scene where they're tumbling down the hill, Buttercup has a beard.

Continuity: When Westley and Inigo are duelling, Westley flings his sword so that it sticks into the ground and then athletically flips from a bar to where the sword is and nonchalantly reaches down and back and takes it out of the ground. But if you watch, he lands too far away from the sword to do this.

Revealing: When Inigo and Westley are duelling, they are making athletic jumps. One does it after the other and when they land you can see the mat wrinkle under the "dirt" on the ground.

Other: When Westley and Buttercup are in the fire swamp and Buttercup is burned for the first time look carefully at the fire spurt, it's several feet away from Buttercup and is clearly too far away to have burned her.

Continuity: When Vizzini is cutting the rope at the top of the cliffs of insanity he cuts it really close to the rock the rope is wound around. In the following shots there is a lot of length of rope between the rock and where it was cut.

Visible crew/equipment: When the ROUS is biting Buttercup's dress (ground level shot), you can see the silhouette of a hand inside, or maybe behind, the dress. Maybe they had to push it up to the mouth because it couldn't grab it?

Continuity: When Westley and Buttercup are walking through the Fire Swamp Westley's hair continually gets better or changes. One scene it is slicked back and another it is in his face or over to one side, etc.

Continuity: After Fezzik has finished dunking Inigo's head in the bucket of water, Inigo has hair stuck across his forehead. While talking to Fezzik Inigo's hair suddenly is all brushed away from his face. Inigo's hair changes back and forth throughout the rest of the scene.

Continuity: After the grandfather has finished reading the book, he stands up to put on his hat and coat. The shot goes to behind him, and we see that he has already put his left arm through the sleeve. Then the shot changes again and we see him from the front as he is sliding his left arm into the sleeve.

Revealing: When Fezzik is pulling everyone up the Cliffs of Insanity, look closely and you will see the cable that is pulling HIM up.

Visible crew/equipment: When Westley and Inigo are duelling at the The Cliffs of Insanity - and as Inigo catches his sword that had been knocked into the air - one can see a portion of a boom mike bobbing down on the left side of the screen. Pan and scan version only.

Visible crew/equipment: There is a scene where the Prince and the Count are talking at the entrance of The Pit of Despair and the sound mike can be seen bobbing around on top. [This is only visible in the original 1980s VHS pan-and-scan version of the film, and is due to the open-matte process that was used to produce the VHS release. See http://www.widescreen.org/widescreen_matted.shtml for an illustration. Still a mistake, but there's why - pan and scan is evil.]

Continuity: When Inigo is lying aginst the wall after Count Rugen has stabbed him in both shoulders, back shots of him show his head is tilted to the left and bobbing while in front shots, he is holding it straight.

Continuity: In the scene where Wesley and Buttercup roll down the hill, when they get to the bottom, they are far apart on the wide shot and close together on the close-up shot.

Continuity: During the scenes when Buttercup wears a red dress (from horseback ride to Fire Swamp), watch her legs carefully. She is wearing red stockings which periodically disappear and reappear.

Continuity: When Fezzik falls to the ground after fighting with Westley, there is a very large rock right next to him.  It is gone in the next shot.

Continuity: In the scene where Inigo kills all of Count Rugen's guards, notice the position of the dead guard in front of Fezzik and Westley. He changes position once after the shot of Count Rugen running away, and again when Fezzik puts Westley on the suit of armour.

Continuity: When Inigo and Count Rugen are duelling in the banquet room, watch the Count's sword: after he stabs Inigo near each shoulder and draws out the sword it is clean.  A moment later, as Inigo falls forward a bit and then rights himself, blood is seen on the Count's sword.  If you watch both their swords during this entire scene you'll see the disappearing/reappearing blood.

Revealing: In the scene before the climb of the Cliffs of Despair after they get off Vizzini's ship the end of the back of the ship suddenly jiggles back and forth like it's made of rubber.

Continuity: When Buttercup finds Westley in the honeymoon suite and jumps on him on the bed, her stockings and shoes are black. When she jumps from the window into Fezzik's arms, her stockings and shoes are white. I doubt she changed in front of Westley, Inigo, and Prince Humperdinck.