There is less low comedy in Macbeth than in any other Shakespearean tragedy, and all of it, aside from the occasional ambiguous remark, is concentrated in a single scene and a single character. The scene is act 2, scene 3, in which the knocking at the gate that has so alarmed Macbeth in the previous scene finally rouses his porter.

The porter is drunk, curmudgeonly, and lewd. He makes a great parade of his irritation at the volume of the knocking, and at having to open the gate so early. When he has done so, he converses with Macduff and Lennox, beginning by remarking how much he had to drink last night, and saying that drink provokes "nose-painting, sleep, and urine." He then turns, inevitably, to the effect of drink on lechery:

Lechery, sir, it provokes, and unprovokes; it provokes the desire, but it takes away the performance: therefore, much drink may be said to be an equivocator with lechery: it makes him, and it mars him; it sets him on, and it takes him off; it persuades him, and disheartens him; makes him stand to, and not stand to; in conclusion, equivocates him in a sleep, and, giving him the lie, leaves him.

The references to equivocation here may be an allusion to the Gunpowder Plot and the Jesuit practice of equivocating when asked difficult questions. The sexual innuendoes, however, are so coarse and obvious that they barely count as innuendoes at all. The porter finds four different ways of saying that drink makes men more lustful but impedes their sexual performance before concluding with another reference to equivocation.

This short interlude of low comedy provides a respite for the audience between two of the most dramatic scenes: Macbeth's murder of Duncan and Macduff's discovery of his corpse. Even in a play of such tragic intensity as Macbeth, two such powerful scenes could not occur in direct succession.