Palivizumab must be administered monthly by intramuscular injection throughout the RSV season to maintain the serum concentration at a level sufficient to provide protection against respiratory syncytial virus (RSV). The objective of this study is to determine factors associated with completing all doses of palivizumab. The method was a survey mailed to the families of 385 high-risk children who were eligible to receive palivizumab at Columbus Children's Hospital in 1998-1999. Seventy-eight percent of eligible children received all doses of palivizumab. The strongest predictor of compliance was parents' perception that palivizumab would protect their child from RSV; 67% of parents in the compliant group reported they believed palivizumab protected their child "a great deal" against RSV compared with 48% in the noncompliant group (p = 0.04). Difficulty with transportation was also a barrier to compliance; 85% of parents in the compliant group reported no difficulty with transportation compared with 65% in the non-compliant group (p = 0.004). An interaction between Medicaid status and parental worry showed that parents whose child received Medicaid and who worried a lot (about their child getting RSV) were more likely to be compliant (Odds ratio = 6.62, p = 0.03). Communication with parents that focuses on the benefit of palivizumab in reducing RSV-associated illness and hospitalizations may increase compliance.