Compared data on gender differences in age at onset and symptomatology of schizophrenia from the World Health Organization (WHO) Collaborative Study for 7 research centers in Western Europe, the Balkan region, and an Islamic region. 277 men and 223 women (aged 15-44 yrs) were studied. Results confirm an earlier onset in men. In the Islamic centers, no relevant gender differences in real age at onset and in symptomatology could be detected as probable causes of earlier hospitalization of women. Major gender differences in symptomatology were found in the Balkans with a high prevalence of delusional symptoms in women and depression in men. In Western Europe, nuclear schizophrenic symptoms were equally prevalent in either sex, while nonspecific symptoms like irritability and tiredness and maladaptive illness behaviors like alcohol abuse and social withdrawal differed between the sexes.