In lower respiratory tract infections, the most frequently isolated organisms are Mycoplasma pneumoniae, Bordetella pertussis, Klebsiella pneumoniae, Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and Proteus mirabilis. In both comparative and noncomparative studies, cefotaxime, a third-generation cephalosporin, has been shown to be effective in the treatment of lower respiratory tract infections. Cefotaxime is effective against a wide range of pathogens, including S pneumoniae, H influenzae, Klebsiella pneumoniae, Escherichia coli, P mirabilis, S aureus, and Streptococcus pyogenes. Good results with cefotaxime also have been achieved in immunocompromised patients and those in intensive care units. In one study of more than 300 patients with severe bronchial infections, an excellent response was obtained in 96.8% of patients treated with cefotaxime. When used in combination with other antibiotics, such as aztreonam or the aminoglycosides, cefotaxime produced bacteriologic cure rates of close to 100% in critically ill patients with nosocomial pneumonia. Studies in the international medical literature have concluded that cefotaxime is a useful drug for the treatment of lower respiratory tract infections.