Objectives: delusional disorder is not a common psychotic disorder, often characterized by single and systematic delusion. The present study was designed to examine delusional disorder in terms of epidemiology, symptomatology and, phenomenology. Method: the subjects were 51 patients (34 male, 17 female, 45 hospitalized, and 6 out patients), who were diagnosed as suffering from delusional disorder on the basis of DSM-IV diagnostic criteria. They were studied for a period of two years at Rooxbeh hospital. The data was collected through a 49 item questionnaire, a Wechsler IQ test, and CT scans. Findings: the most prevalent delusions were found to be persecutory and jealously delusions (49.2% and 40.7% respectively). The average age for the onset of the disorder was about forty one. 20% of the patients were from low socio-economic conditions. In 45% of the cases, severe mental stress was noticed in the background. Traces of mental disorder in the family history, organic disease, and substance abuse were estimated to be 30 %. Results: the pattern of delusional disorder in this study seems not to be much different from that of similar studies.

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