Successful treatment of community-acquired pneumonia (CAP) can have substantial implications. As rates of antibiotic resistance of Streptococcus pneumoniae--the most common pathogen of CAP-increase, so does the likelihood that first-line pharmacotherapy will fail. Thus, the cost effectiveness and budgetary effects of treating CAP with amoxicillin/ clavulanate (AMX/CLA) extended-release (ER) and clarithromycin ER were analyzed. The model considers incidence of macrolide and AMX/ CLA-susceptible and nonsusceptible S. pneumoniae in empiric therapy. Clinical cure rates from multicenter clinical trials and published literature were used to calculate average treatment costs and success. Amoxicillin/ clavulanate ER resulted in a higher percentage of patients cured compared with clarithromycin ER (88.7% vs. 82.4%, respectively) and lower average per-patient treatment costs (dollar 437.70 vs. dollar 548.14, respectively).