A cost-effectiveness analysis was performed for three antibiotic drug therapies in pneumonia and bronchopneumonia: broad spectrum penicillins, III generation cephalosporins and ceftriaxone. The study was based on records from 117 patients in 9 general medical departments in North and Central Italy during 1989. Costs included direct cost of drugs, staff, accommodation, and other hospital costs. Effectiveness was measured radiographically as clinical cure, interruption of therapy or death. The effectiveness and shorter duration of therapy with ceftriaxone in respect to the other treatments, produced a 15.18% savings of hospital resources compared with other III generation cephalosporins, and a 14.76% savings compared with broad spectrum penicillins. This is a provisional conclusion requiring confirmation with a larger number of patients and randomized trials.