Causal attributions for positive and negative hypothetical social events made by paranoid patients, depressed patients, and nonpatient participants were examined via a novel measure of causal locus, the Internal, Personal and Situational Attributions Questionnaire. Depressed patients tended to attribute negative social events to internal (self-blaming) causes. Nonpatient participants and patients with delusions of persecution tended to avoid such self-blame. However, whereas nonpatient participants tended to choose situational or circumstantial external attributions, paranoid patients tended to choose external attributions that located blame in other individuals. These findings support R. P. Bentall, P. Kinderman, and S. Kaney's (1994) defensive attributional model of persecutory delusions, suggest some modifications to that model, and have implications for the understanding of the relationship between causal attributions and social and self-perception.