The value of a single daily injection of 2 g ceftriaxone in lower respiratory tract superinfections was demonstrated in 22 patients in a neurosurgical intensive care unit. Catheter bronchial samples were submitted to bacteriological investigation and ceftriaxone concentrations were determined in serum and bronchial secretions. Results show that sustained efficient levels of ceftriaxone were achieved and enabled the successful treatment of lower respiratory tract infections due to susceptible pathogens.