Three examples of dramatic irony in "The Cask of Amontillado" include:
the carnival scene where Montresor fabricates a story about Amontillado wine. The reader knows that he is manipulating Fortunato, who is completely unaware of Montresor's true intentions;
when Montresor feigns concern for Fortunato's health and suggests that they leave the vaults; and
when Montresor toasts to Fortunato's long life.
In each instance, Fortunato fails to recognize that Montresor is plotting his demise.