STUDY OBJECTIVE:The aim was to examine if there is an effect of fathers' age and of birth order on the occurrence of congenital heart disease. DESIGN:This was a hospital based case-referent study including use of birth defects surveillance data. SUBJECTS:Subjects were 497 cases of congenital heart disease aged between 3 months and 5 years, born in Beijing and Hebei Province, China; 6222 children without congenital heart disease serve as reference baseline. MEASUREMENTS AND MAIN RESULTS:With stratified analysis and logistic regression analyses, congenital heart disease was found to be associated with fathers' age less than 25 years (odds ratio 2.63), independent of mothers' age and of birth order. There was also evidence to show a higher birth order effect on the occurrence of congenital heart disease independent of parental ages. CONCLUSION:Higher birth order and fathers aged less than 25 years were both independently associated with some categories of congenital heart disease and with congenital heart disease overall.