The incidence of bacterial species and their susceptibilities to ceftriaxone and other beta-lactams from patients with community-acquired infections were evaluated in a multicenter study over a 4-month period. A total of 5,768 bacterial isolates were classified according to whether the patient had been previously hospitalized or had received antibiotic treatment. The most relevant findings were the presence of 33.8% penicillin-resistant Streptococcus pneumoniae isolates, 25% beta-lactamase-producing Haemophilus influenzae isolates, and 36.4% amoxicillin-resistant Escherichia coli isolates. All of these bacteria were fully susceptible to ceftriaxone. Nosocomial multiply-resistant bacteria, and particularly methicillin-resistant S. aureus, were found, as expected, at a higher frequency among previously hospitalized patients. However, such bacteria may be present in the community; their incidence is high in particular clinical settings, and such bacteria should be considered when one is choosing a first-line therapy for the treatment of severe infections.