SM-4300, a new developed immunoglobulin preparation with ion-exchange treatment, was used intravenously for 12 infectious diseases. These 12 cases (under 10 years old) were including 4 sepsises, 3 pneumonias, 1 pyothorax, 1 ventriculitis, 1 purulent meningitis, 1 aseptic meningitis and 1 cellulitis. To evaluate the effect of SM-4300, 2 cases were excluded from evaluation because of blood transfusion or immediately death. Since antibiotics were used at the same time, it was surely difficult to evaluate the effect of SM-4300. In 10 cases, 2 cases were excellent effective, 4 cases were fairly effective and others were not effective. Including fairly effective cases, the rate of efficacy was 60%. In all cases, there were no significant side effects regarding clinical findings and laboratory examinations. SM-4300 may be available for severe infectious diseases with antibiotics therapy.