In Ancient Greek, an impolite order can be uttered by means of a negative interrogative in the future tense (οὐκ ἐρεῖς; ‘Won’t you talk?’). The aim of this paper is to understand to what extent this type of utterance is impolite, and to explain how such a conventional and indirect order can frequently take on an impolite meaning. For this purpose, data are taken from classical drama (Aristophanes’ and Euripides’ plays). Drawing on criteria put forward by recent work on impoliteness, this study provides an accurate description of uses in discourse, in order to establish that this conventional order is never used with a polite intention, but regularly as an impolite order. Impoliteness can be explained by the locutionary form which gives an orientation to the interpretation of the utterance: an indirect and conventional expression cannot be polite if the locutionary meaning is opposed to it.