During conversation, speakers and listeners act on certain basic assumptions, which enable them to communicate swiftly and seemingly effortlessly (Grice, 1975). The speaker, for instance, is supposed to say no more, but also no less than is necessary in a given conversational context (Maxim of Quantity). The present study looks at how language users react when this pragmatic assumption is violated. Participants were presented with written mini-dialogues while their ERPs (Event-Related brain Potentials) were measured. Dialogues in the violation condition, where the answer did not meet the quantity requirements, differed from control dialogues in three different time-windows, time-locked to the presentation of a critical word. Violating the Maxim of Quantity was signalled immediately and gave rise to effortful processing at different levels of representation.