Blood samples were collected from 140 institutionalized children aged 0~9 at Goyang gun. Kyunggi Do, Korea. The venous blood was taken and isolated serum was used for Haemagglutination(HA) test.1. Out of 140 samples, the positive rate of HA titer was 35.7 per cent. No significant differences was recognized by sex gropus. 2. When subdivided into the 0~4 and 5~9 years age groups, the positive rate obtained 30.4 per cent and 34.1 per cent respectively, which was no significant difference. 3. The positive rate of HA titirs in various diseases was 31.0 percent in total, being 50 per cent in mental retardation cases, 100 percent in delayed speech and hearing loss.