This paper deals with the question of negation and mood in Modern Greek verb complementation where there is a choice between an indicative and a subjunctive complement, in particular those with the verb pistévo (πιστεύω) ‘think, believe’, but also nomízo (νομίζω) ‘think, believe’, kséro (ξέρω) ‘know’, thimáme (θυμάμαι) ‘remember’, vlépo (βλέπω) ‘see’, akúo (ακούω) ‘hear’, and vrísko (βρίσκω) ‘find’. It presents the result of an empirical study of pistévo, based on an investigation undertaken in the Hellenic National Corpus ( HNC) of sentential complements following pistévo. The factor of negation in the matrix is investigated along with two other factors, hypothesized to be of interest, namely first person singular of the present tense in the matrix and second person (singular and plural) in the complement. As was expected, neither any of the three factors individually or any combination of the three can be considered decisive for the choice of mood. What seems to be certain, however, is that the combination of all three constitutes a context that favours the subjunctive and in one case actually seems to exclude an indicative complement, namely when the illocutionary force of the utterance is that of a question, more or less rhetorically eliciting feedback. It thus does not seem to be the presence of the negation, nor any other syntactic factor, that actually triggers the subjunctive with this verb in some contexts, but a particular speech situation (where the three investigated factors are typically present). That is, the prerequisite is not syntactic, but pragmatic.