A study sample of 88 delusional patients has been examined prospectively from first admission and during three personal follow-up sessions. After 8 years of observation, the diagnostic distribution is presented according to the ICD-10 and the DSM-III-R classification systems, among which a large degree of agreement is found. Schizophrenia turned out to be the most frequent diagnosis but almost half of the patients belong to another diagnostic category. Diagnostic assignment was changed in only a few patients when compared to the time of discharge after the first admission. From the time of index admission, the patients' preceding course and global functioning differ. A major finding is the fact that in general short-term course and outcome are very similar to those of medium-term observation. Forty-three per cent of the patients still alive remained delusional throughout the observation period. Delusional beliefs do not persist in all patients with the diagnosis of persistent delusional disorder. Most patients with continuous delusional beliefs belong to the diagnostic category of schizophrenia. Global assessment functioning at 8-year follow-up is: schizophrenia, 35; affective disorder, 82; persistent delusional disorder, 50, and acute and transient psychotic disorder, 72.