OBJECTIVE: We wanted to study the prevalence and characteristics of dangerousness among female psychiatric patients. METHOD: A national survey was performed in Norway, covering all psychiatric in- and out-patient units. RESULTS: There were 329 persons reported to have a psychiatric disorder and to satisfy our criteria for dangerousness, giving a total prevalence of 9.9/100000 adults. There were 54 women, giving a female prevalence of 3.1/100 000. When compared to a matched sample of the men, fewer women were out-patients or had had jail sentences. We found no sex differences with regard to frequencies of psychosis, mental retardation, personality disorders, or drug or alcohol abuse. The women had an increased frequency of suicide-related and self-injurious behaviours and previous commitment for arson. CONCLUSION: The prevalence of women with psychiatric disorders who are considered to be dangerous was 3.1/100 000. The dangerous men did not show higher frequencies than the women for psychopathology, drug abuse, behaviour or criminality.