The objective of the study were to determine if nationally recognized community-acquired pneumonia (CAP) guidelines (specific to antibiotic therapy) were being followed and to identify outcomes of treatment in hospitals that are VHA members. This was a prospective study using a medication use evaluation in an inpatient setting conducted in 46 institutions in the United States during the 1998-1999 CAP season. The subjects were 875 adult patients (> or =18 years of age) admitted from the emergency department or ambulatory care setting with a chest X-ray-confirmed diagnosis of CAP. Treatment pathways were in place in 58.7% (27/46) of institutions, with 18.3% of patients treated according to pathways. Twenty-seven percent of patients were PSI class I or II. A pathogen (blood or sputum) was identified in <10% of patients. The first dose of antibiotic was administered to patients 65% of the time in the emergency department. Antibiotic therapy in 592 of the 694 admitted to a general medical unit (mortality rate, 3%) complied with 1998 Infectious Diseases Society of America (IDSA) guidelines compared with 26 of the 65 admitted to the intensive care unit (ICU) (mortality rate, 4.6%). In patients admitted to other nongeneral medical, non-ICU areas, IDSA guidelines were followed in 95% of the patients. Mean length of stay and mortality for PSI classes I-V were 4.5, 4.6, 6.9, 6.2, and 7.1 days, respectively, and 0%, 0.7%, 1.1%, 2.5%, and 10.5%, respectively. Antibiotic therapy was modified in 733 of 875 patients. Approximately 90% of patients were eligible for conversion to oral (per os) therapy before discontinuation of parenteral (intravenous) antibiotics (mean time to eligibility, 1.8 days of parenteral antibiotics), with conversion in 65% (mean time to conversion to oral therapy, 4.6 days). Resolution of CAP occurred in 92% of patients; deterioration was more common in PSI class IV and V patients. In conclusion, inhospital mortality rates for all PSI classes were similar to those found in other recently conducted studies despite limited adherence to pathways. Greater use of treatment guidelines for patients admitted to the ICU and awareness of the intravenous to per os antibiotic conversion process are suggested.