This article examines scatology in Aristophanes Assemblywomen, and argues that the play sets out to subvert comedy's normal scatological poetics. Old Comedy is usually a genre characterized by corporeal and scatological freedom. The constipation scene in Assemblywomen 311–73 is therefore highly unusual, since, while its language is scatological almost to the point of excess, it spotlights not scatological freedom but scatological obstruction. This article argues that this inversion is expressly linked to the play's reversal of gender roles as part of its ‘women on top’ plot, which is in turn conceived as a direct challenge to Old Comedy's normative poetics. The article further suggests that recognizing the Assemblywomen's less than straightforward relationship to the norms of Old Comedy may help us to reassess how, and indeed whether, we should use Aristophanes’ plays to make conjectures about the genre as a whole.