A critical human ability is to revise one's own beliefs in light of contradictory evidence. Many argue that it is precisely this ability that is missing among schizophrenic patients and that such a deficit could be the source of delusions. However, no study, as far as we know, has ever directly investigated belief revision ability in schizophrenia. Thus we introduced several tasks requiring patients to revise their beliefs. First, the Wason's hypothesis testing task (the 2-4-6 task) was used. Subjects have to discover a simple rule known by the experimenter concerning a series of three numbers. A belief revision deficit would suggest that patients are incapable of abandoning their initial hypothesis and finding such a rule, since this requires flexible evaluation and hypothesis testing. Second, the way patients treat advice was explored in a task involving encyclopaedic knowledge. According to the belief revision deficit theory, patients should exhibit no change in their answers when they encounter advice that differs from their own view; they should also have a high degree of confidence in their responses. Finally, a Myside bias task was used to see whether patients exhibit closed-mindedness concerning everyday topics. A belief revision deficit would predict that patients would show an important Myside bias, thus being incapable of envisaging arguments against their beliefs. Surprisingly, our findings suggest that deluded schizophrenics are in fact able to revise their beliefs in the light of evidence and alternatives. Further research is needed to establish the causes of delusions.