Twenty-five hospitalized neonates, each with two or more serious symptomatic infections, were given netilmicin by intramuscular injection. The antibiotic was administered usually at 1.5 or 3.0 mg/kg twice a day (q 12 hr) for 7 to 13 days. At the end of therapy the signs and symptoms of infection were completely resolved in twenty-four of the twenty-five patients and markedly improved in the remaining one. Thirty-five causative organisms were isolated from 30 of the 59 infection sites; after netilmicin therapy 31 causative organisms were completely eliminated and 4 were markedly reduced in number. One of the babies had a slight increase in serum creatinine level, possibly related to therapy, and a mild transient rash which was doubtfully related to netilmicin. None of the other neonates had adverse reactions.