Ceftriaxone sodium, a new cephalosporin with a very broad spectrum of action and a very long serum half-life, was administered to 127 patients in the treatment of 133 severe infections at our institution in Lausanne, Switzerland. Eighty infections had previously been treated unsuccessfully with other antimicrobials to which the pathogens were most often resistant. Sixty-five episodes were treated with two daily injections until there was an improvement in the patient's clinical condition, while 67 infections were treated from the start by a single daily injection. The results in the two groups were similar. One hundred fifteen infections (86%) were cured or improved, ten (8%) did not respond to therapy or recurred, and eight (6%) were not evaluable. The treatment was well tolerated, even by the 18 patients who received the drug for more than four weeks. The administration of a single daily dose instead of four doses as with standard antibiotic regimens produced a saving of Sfr 84,000 (+42,000) in the 127 patients. The single daily dose also made it possible to treat 25 of the 127 severely ill patients as outpatients, with a saving of Sfr 388,500 (+195,000) with respect to the hospital costs that would have been incurred for the same time period.