In the summer of 1957, the citizens of Finland were subjected to a severe and dramatic Type A2/Singapore influenza epidemic. Saxen et al (1960) studied the teratogenic effect of the influenza epidemic. They observed a population of 6075 consecutive deliveries in the First and Second Women's Clinic of the University Central Hospital in Helsinki in late 1957 and early 1958. Timing of the flu infection was recorded for each women. Diagnoses were recorded for all members of the Helsinki 1957 epidemic cohort who had been admitted to any of the eight psychiatric hospitals in the greater Helsinki area. Controls for the study comprised all subjects admitted to these same hospitals born in the same months of the year as Index subjects but in the 6 years preceding the epidemic. The total study sample comprised 1781 individuals. The results showed that those who experienced the epidemic in their second trimester of gestation suffer a significantly higher proportion of adult schizophrenia diagnoses than their controls. Subjects exposed during the first or third trimesters do not show such an increase. The Index subjects tended to receive a disproportionate number of Other (295.8) and Unspecified (2895.9) ICD-8 schizophrenia diagnoses. They also tended not to be diagnosed according to classical subdiagnoses. These results strongly suggested the value of further study of the 1957 Helsinki cohort. The current proposal has the following specific aims: 1) to establish more precisely the critical period in gestation during which fetal viral infection is associated with an increased risk of adult schizophrenia; 2) to identify in the Saxen cohort those 2nd trimester individuals with positive maternal flu symptoms during the epidemic and check whether they exhibit an elevated rate of schizophrenia diagnoses; 3) to obtain in the psychiatric diagnoses of the Index and Control parents and siblings in order to test the hypothesis that 2nd-trimester viral infection only increases the risk of schizophrenia in those genetically predisposed; 4) if possible, to develop a "symptom picture" of "viral schizophrenia" based on various clinical tools (SADS-LPSE), Personality Disorder Examination, Affective Flattening Scale, Scale for Assessment of Thought, Language and Communication, and Hospital Chart Inventory).