A study was carried out during 1976 to 1982 to determine the immune status against poliomyelitis of 1-36 months old children from several districts of Indonesia. A total of 1661 sera were collected and tested by micro serum neutralization test against 100 TCID 50 polio virus in monkey kidney cell cultures. The results show that in the year 1976, in Jakarta, 78.6 % 1 —12 months old children were triple negative, whereas in 1980, the percentage of triple negative children of similar age group were 23.4% and 15.3% respectively. Triple negative children of similar age group in Purwakarta (1978) 20.5% and 14.3 %; in Cimahi (1978) 20.6 % and 17.8 %; in Banjarmasin (1981) 23.4 % and 11.9 %; and in Jambi (1982) 61.4 % and 54.6 % respectively. The proportions of triple positives are higher in areas which have experienced a recent epidemic or in areas where the population uses river water for household purposes. The significance of these results are discussed and it is recommended that children should be vaccinated against polio before the age of 2 years.