The efficacy of ceftriaxone, 1 g given intramuscularly once daily, was evaluated in 38 patients with pneumonia (n = 11), pulmonary empyema (n = 2), bronchitis (n = 4), tonsillitis (n = 9), sinusitis (n = 7), and otitis (n = 5). Causative organisms were Streptococcus pneumoniae (n = 11), viridans type streptococcus (n = 1), Haemophilus influenzae (n = 6), group A streptococcus (n = 10), Staphylococcus aureus (n = 3), Klebsiella pneumoniae (n = 2), Pseudomonas aeruginosa (n = 1), Escherichia coli (n = 2), Proteus mirabilis (n = 1), and Proteus vulgaris (n = 1). Sterilization of infected foci was obtained in 89.4% of those treated, with clinical recovery in 86.8%. The ceftriaxone regimen was well tolerated.