Abstract: The main aim of this study was to investigate whether or not subtypes of delusional disorder diagnosed by DSM-III-R show differences in age at onset and sex distribution. All out-patients first seen at the psychiatry clinic between 1989 and 1994 were diagnosed by DSM-III-R. Of 4144 out-patients, 51 patients (1.2%) were selected as having delusional disorder, and the demographic data and clinical profiles for these subjects were evaluated prospectively by the psychiatrists. Females outnumbered males by a ratio of 3:1. The type of delusional disorder most frequently encountered was the persecutory type, followed by the somatic type, jealous type and unspecified type. The age at onset differed significantly according to the type of delusional disorder, the oldest age at onset being associated with the persecutory type, and the youngest with the somatic type.