Abstract Using three different schizophrenic populations from Northern Finland, gender differences in some sociodemographic variables, age at onset, incidence, treatment, outcome and deinstitutionalization of schizophrenia were examined. The first study population comprises the Northern Finland 1966 Birth Cohort, which is an unselected, general population birth cohort. We followed prospectively 11017 subjects from 16 to 28 years of age by means of the Finnish Hospital Discharge Register. From this study population gender differences at the age of onset and incidence of schizophrenia were calculated. The second study population was formed of 1525 patients who had their first treatment episodes at the closed therapeutic community ward situated at the Department of Psychiatry, University of Oulu during 1977 - 1993. Gender differences were assessed in relation to age at first admission, some sociodemographic variables, degree of active participation of the patients in individual, group, and milieu therapy and institutional outcome of the patients with schizophrenia. The third study population consisted of all the 253 long-stay psychiatric inpatients treated for at least six months without a break during 1992 in the Department of Psychiatry, Oulu University Hospital. From this study population gender differences at the age of onset and in relation to some sociodemographic and clinical variables were studied. The placements after the last discharge and at the end of the follow-up and factors predicting hospitalization after the follow-up were also monitored. There were no statistically significant gender differences regarding age at onset in any of these three different study populations. The time lag between the first psychotic symptoms and the first psychiatric hospitalization was minimal. In the Northern Finland 1966 Birth Cohort study the annual incidence rate of DSM-III-R schizophrenia was relatively high, 7.9 per 10 000 in men and 4.4 in women by the age of 28. In men it was highest in the age group of the 20-24 year-olds while in women the peak occurred earlier in the age group of the 16-19 year-olds. In the Therapeutic community study there were no statistically significant gender differences in the sociodemographic variables, in the length of stay and in the number of treatment episodes in this ward in any of the diagnostic groups. Differences with regard to male and female participation in individual, group and milieu therapy and the institutional outcome were minimal, some trends, however, favoring females. In the long-stay patients study almost two-thirds of these patients were men. Very few gender differences were found in relation to sociodemographic and clinical characteristics or regarding the utilization of psychiatric hospital care. About 70% of the long-stay patients were discharged during the four year follow-up period and only 15% were able to live without continuous support. Marital status (being not married), dwelling place (living in city), absence of negative symptoms and severity of the illness were associated with hospitalization at the end of the follow-up. Gender did not predict hospitalization at the end of the follow-up period. The results of this study indicate that there are probably different subgroups of schizophrenia in which there are no gender differences regarding age at onset and in the clinical picture of the disturbance or there are regional differences in the manifestation of the illness. In Finland patients are hospitalized earlier after the onset of the first psychotic symptoms than in many other countries. According to the Northern Finland 1966 Birth Cohort study the incidence of schizophrenia is higher among young men than women and the total life-time incidence of schizophrenia may be smaller in women. The results from the Therapeutic community study suggest that therapeutic community treatment may level out the gender differences in the treatment process and outcome. The long-stay patient study showed that long-term patients are dependent on considerable support and that the most seriously ill patients are in fact in hospital. Alternative residential facilities have been a presupposition to the deinstitutionalization of the long-stay patients.