Ampicillin-sulbactam was compared with cefamandole in the treatment of bacterial pneumonia in elderly patients. Clinical improvement ard hospital discharge occurred in 25 of 26 patients in the ampicillin-sulbactam group vs. 20 of 23 in the cefamardole group (P >.06). Etiologic agents isolated from adequate sputum samples were more likely to be eradicated with ampicillin-sulbactam (24/26) than with cefamandole (15/23) (P <.05). The most common organisms isolated from elderly patients with pneumonia included Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae. M. catarrhalis was eradicated from sputum in 2 of 5 patients treated with cefamandole, and these isolates had relatively high minimal inhibitory concentrations (8 to 16 μg/mL).