141 newborn with purulent surgical infection were under observation. In 73 the inflammatory process was not induced by Pseudomonas aeruginosa in 68 the infection was caused by the blue pus bacillus. Bacteriological and immunological examination was conducted, including that with the use of enzyme immunoassay, to monitor the optical density of anti-pyocyanea antibodies during the course of the disease. It was found that the serum of a healthy newborn baby contains antibodies to Pseudomonas pyocyanea and did no differ from that of healthy older children in the level of anti-pyocyanea antibodies. The increase of the level of anti-pyocyanea antibodies in response to infection with Pseudomonas pyocyanea is twice less in newborns than older children with this infection. The use of specific plasma is much more effective than the administration of nonhyperimmune plasma. The efficacy of treatment with anti-pyocyanea plasma is determined by the level of anti-pyocyanea antibodies produced in the patient as a result of plasmatherapy rather than the volume of the dose given for the course.