A statistical study is made of the children born up to first admission to married women hospitalized for serious mental disease in Norway 1936-1975, 30,428 women were registered, with a total of 60,916 children. This observed number of children was related to the number to be expected if the fertility of the patients had been equal to that of a corresponding sample of the general population. The relative fertility (number of children observed per 100 expected) was found to have increased moderately from 72.4 in 1936-45 to 83.6 in 1966-75. There was no difference between the diagnostic categories, in particular not between schizophrenia and manic-depression. It is pointed out that individuals with a psychotic parent may represent a high-risk group because of their social and personal situation. Our material indicates that each year 1,800 children are born in Norway who during their childhood or adolescence were exposed to this particular risk.