Parenteral administration, intravenous followed by intramuscular, or intramuscular alone, cured thirty children with pneumonia and empyema caused by S. aureus, D. pneumoniae, Klebsiella sp. and other gram-negative bacteria, within one to three weeks. Pathogens disappeared from pleural pus in all empyema cases within the first forty-eight hours of treatment. Following intravenous administration peak plasma levels ( 117 mcg/ml) were obtained in five minutes, and following intramuscular injections peak plasma levels ( 55 mcg/ml) were obtained in one hour. High concentration levels were observed in pleural pus ( 23-37 mcg/ml) in two hours. The drug was very well tolerated both locally and systemically.