OBJECTIVES: Palivizumab is used for respiratory syncytial virus (RSV) prophylaxis in high risk children. Data on seasonality, risk factors, and outcomes are necessary to evaluate the impact of palivizumab on the incidence of RSV infections, minimize healthcare resources and identify which infant sub-sets are receiving prophylaxis.To determine current usage of palivizumab prophylaxis, compliance patterns, hospitalization rate (HR) and outcomes in children at high-risk of respiratory syncytial virus (RSV) infection through a Canadian Registry Database (CARESS). METHODS:  A prospective, study of infants who received at least 1 dose of palivizumab in the 2006-2009 RSV seasons across 27 sites. Neonatal and demographic data were collected upon enrolment. Parents/caregivers were contacted monthly for data on palivizumab utilization, compliance and outcomes related to any respiratory tract events. RESULTS: A total of 4926 infants aged 2 days - 47 months (mean=5.4 months) were enrolled. Participants were typically male (57.1%) and Caucasian (70.8%). Gestational age (GA) was 32.2±4.6 completed weeks. 3480 (70.6%) premature infants received palivizumab (≤ 35 completed weeks GA), 403 (8.2%) required O2, 471 (9.6%) had congenital heart disease and 572 (11.6%) were prophylaxed for other risk factors. On average patients received 3.7 ± 1.5 injections, with 17,982 doses given overall. There were no drug related serious adverse events.296 infants required 357 hospitalizations for respiratory tract infections with a hospitalization rate of 6.0%. There were significant differences between indications for palivizumab (chi-square=71.8, p<0.005).The overall RSV positive HR was 1.38%. Hospitalization rates were highest in infants of aboriginal descent (15.0%, chi-square = 22.2, p<0.005). Hospitalized infants had a lower percentage of compliant injections (62.8% versus 68.6%, p=0.003). CONCLUSIONS:  The RSV HR in the 2006-2009 RSV seasons resembled several published reports (range 1.3%-5.3%). RSV HR may be decreasing because of compliance with palivizumab prophylaxis, variability in RSV epidemiology, hospital admission criteria and preventive education.