According to the literature, schizophrenia begins in men earlier than in women. It has been argued that the gender-bound age difference is due to the protective antidopaminergic effect of estrogens in women. However, the effect of gender on the age of onset may vary between different types of schizophrenias, and can also be modulated by marital status and by age at onset of illness. Comprehensive data were collected on 3306 DSM IIR schizophrenia patients, aged 15-64 years, who had been discharged from psychiatric hospitals in Finland in 1982, 1986 and 1990. The age of onset of illness (AOI) was defined by the age at the first admission (AFA). Male patients were admitted earlier than female patients, and a small second peak in women appeared at the age of 40-44. However, there were no gender differences in AFA within diagnostic subgroups, except in paranoid schizophrenia in which AFA was lower in men than in women even when marital status was taken into account. Within paranoid schizophrenia, this effect of gender was significant only in those of the patients whose AFA was higher than 30 years. It is suggested that there is no gender difference in AOI in early onset schizophrenia. In later onset, paranoid schizophrenia, the illness seems to manifest in women later than in men.