The persistence of delusional beliefs may to a marked degree influence the patients' global functioning. It is therefore clinically relevant to search for predictors of this course. In a study sample of 75 delusional first admitters such demographic, social and clinical variables were investigated which concern the course during 8 years. A number of variables had predictive value, e.g. characteristics of the delusional beliefs themselves such as theme and dimensions, absence of mood disturbance and subjective thought disorder but not hallucinations. The variables of diagnosis (schizophrenia according to the ICD-10 or the DSM-III-R at discharge from first admission) was a highly significant predictor of which only the following variables had a significant and independent predictive value: living alone, no psychosocial stressor, main delusion of persecution, and main delusion other than reference. In spite of the diagnostic uncertainty among first admitters the new systems of classification provide diagnostic categories as the most significant predictor of persistent delusional beliefs. Two logistic regression models for prediction are presented. In the presence of all independent predictors, the persistence of delusional beliefs is predicted for 94% of the present patient sample.