This experiment has been made to evaluate the distribution of OEP-HA titer, protease-HA titer and elastase-HA titer of antibody which are the common antigen of Pseudomonas aeruginosa in the serum of healthy mother-newborn infant-pairs, term pregnancy women and under 7 month old infants. By analysing the normal limt of these antibodies, it is expected that the result can be clinically applicable to the diagnosis, management and prevention of Pseudomonas aeruginosa infection, which shows rapid increase nowadays, 1. The Anti OEP-HA titer showed under 1:8, a very low titer, in 73% of cord sera group, but over 1:32 in 68% of mother sera group. 2. In healthy mother-newborn infant-pairs group, the anti OEP-HA titer of mothers showed 1:56, 48, much higher than that of newborn infant, 1:16.42. from which it can be concluded that their titer has no relation between the two. 3. The anti OEP-HA titers of healthy mother and term pregnancy women showed 1:56.5 and 1:53, 4, respectively, which are very similar to each ether, but in infant group, the titer showed 1:33, 51 higher than that of cord sera, 1:16.42 4. The anti protease-HA titer showed under 1:8 in 64-77.5% of total cases, which is lower than that of anti OEP-HA titer. 5. The anti elastase-HA titer showed under 1:8 in 93.75% of cord sera group and in 70.27-76.37% of infant, term perenancy women and mother group, but in infant group, the anti elastase-HA titer showed 1:16.56 higher than that of cord sera group 1:8.5.