OBJECTIVES: Millions of cases of CAP are reported in the US annually. The cause can be bacterial or viral. RSV is one cause being examined more closely in adults, specifically in the elderly. This study estimates the direct medical costs of treating an episode of RSV-related CAP in adults (age = 18 years). METHODS: Cases were identified by principal ICD-9 diagnosis code. Residential care facility patients were excluded. As few RSV cases (ICD-9 480.1) could be identified, they were combined with cases of viral CAP, pathogen unspecified (ICD-9 480.9) to form the RSV group. Resource use and cost profiles for inpatient and outpatient management were developed and weighted to determine a mean overall episode cost. The inpatient cost profile was comprised of hospital, post-discharge care and readmissions within 60 days of CAP diagnosis. Inpatient costs and discharge patterns were based on discharge data from five US states. State ambulatory care and emergency room databases were primary sources for outpatient profiles. Inpatient versus outpatient management proportions were derived from literature. Cost estimates are reported in 2001 US$. Charges were adjusted by means of a cost-to-charge ratio. RESULTS: Of the 1,968 RSV CAP inpatient cases identified, 58% were = 65 years old. The mean length of stay was 5.6 days. The mean episode cost for those treated as inpatients was $13,187. Hospital-related costs comprised 75% ($9,939) of that cost. The typical cost of outpatient management was $550. On average, those treated initially as outpatients but subsequently hospitalized accrued $13,888 per person. The mean overall cost for an RSV-related CAP episode was $3,194. CONCLUSIONS: RSV-related CAP cases managed as inpatients are substantially more costly. Initiatives to treat more patients as outpatients should lead to lowering the overall episode cost. These costs provide valuable inputs for economic analyses of viral CAP-related vaccines and treatments.