In autumn of 1976 a study was performed with Gripovax (RIT 4050) in 126 schoolchildren in Vienna. Sixty-one of the children were 10 to 14 years old and 65 were 7 to 10 years old. The study was initiated in the older group (10-14 years old) by transnasal administration of a single dose of vaccine; 23 children received a second dose 7 days later. Symptoms were recorded daily up to the 7th postvaccinal day. 53 out of 61 vaccines did not report any symptoms during the 7 day postvaccinal period. 8 complained of mild and transient nasal stuffiness and only 1 child had a rise in temperature (37.8 degrees C). In a second group (7 to 10 years of age), 65 children received 2 doses of the vaccine at a 7 day interval. No symptoms were recorded in 57 subjects and only 8 reported mild and transient nasal stuffiness. Hemagglutination inhibition (HI) antibody titers were determined before and after vaccination. In the older age group (10-14 years), after one dose of vaccine (vaccinees with prevaccinal titers less than 1:20), seroconversion occurred in 20 out of 28 (71.4%) and after two doses, in 18 out of 21 (85.7%). Children aged 7 to 10 years received both doses of the vaccine. In subjects with prevaccinal titers less than 1:20, seroconversion occurred in 40 out of 43 (93%). Geometric mean of titers (GMT) before and after one dose was 24.3 and 97.4, respectively. The GMT of those children who received two doses (both age groups) was 30 preceding and 185 after vaccination.