OBJECTIVES: Our objectives were the following: (1) to describe the sociodemographic factors, vaccine beliefs, and behaviors that are associated with parental opposition to compulsory vaccination, and (2) to determine if the availability of a philosophical exemption in a parent's state of residence is associated with parental opposition to compulsory vaccination. METHODS: Data from the 2002 HealthStyles survey were analyzed. Chi-square analysis was used to identify significant associations between belief and behavior questions and opposition to compulsory vaccination for school entry. Multivariate logistic regression was conducted using significant variables from the bivariate analysis to identify independent predictors of opposition to compulsory vaccination among surveyed parents. RESULTS: Of respondents with at least one child aged < or = 18 years living in the household (n=1,527), 12% were opposed to compulsory vaccination. Survey results indicate that a parent's belief regarding compulsory vaccination for school entry is significantly associated with beliefs in the safety and utility of vaccines, as well as intention to have the youngest child fully vaccinated. Residence in a state that permits philosophical exemption to vaccination also was significantly associated with a parent's opposition to compulsory vaccination for school entry. CONCLUSIONS: Providing basic information to parents regarding vaccines and vaccine-preventable diseases may help reduce opposition to compulsory vaccination by reinforcing the safety and importance of routine childhood vaccinations.