OBJECTIVES To estimate the proportion of a population receiving RSV prophylaxis, proportion selected for prophylaxis but not meeting American Academy of Pediatrics guidelines (AAP), and fractions of these and the total population hospitalized for RSV bronchiolitis or pneumonia. METHODS The study sample consists of all neonates born into a geographically defined subset of a commercially insured population who had medical claims extending from birth through one or two of five RSV seasons between Fall 2003 and Spring 2008. An AAP-based coverage policy was in effect throughout but prior authorization (PA) required only during the latest seasons. Patients with/without claims for prophylaxis and/or RSV-coded hospitalization are categorized by birth weight, age, and information from PA and claims. RESULTS A total of 44841 neonates were followed through one (10.6%) or two (89.4%) seasons (79253 child-seasons of administrative claims). Counting each once per season, there were 939 cases that received RSV prophylaxis of which 51% had PA approval and 49% had not required PA. Another 216 cases were denied coverage after PA. Additional patients had partial denials for requests for palivizumab starting before or continuing after the RSV season. There were 481 hospitalizations coded for RSV: 20 cases that received palivizumab, 3 of the denied cases, plus another 458 that had not received prophylaxis (of which 93% had normal and 5% moderately low birth weight, and none had claims evidence of chronic lung or congential heart disease). Estimated population RSV hospitalization rate per season was 18.4, 3.6, and 1.7 per thousand age < 6, 6-12, and 12-24 months, respectively. CONCLUSIONS In this population, a substantial fraction of patients selected for palivizumab, and most patients hospitalized for RSV, do not meet AAP criteria for prophylaxis.