Congenital heart defects (CHD) are among the most common birth defects, occurring in 5 to 10 per 1000 live births. This substantial variation in the reported epidemiology of CHD is due to differences in applied methodologies. An increasing total prevalence of CHD has been recently reported, mainly due to increase in prevalence of small defects easily diagnosed by echocardiography, as well as an increase in prevalence of conotruncal defects and atrioventricular septal defects.In order to provide a comprehensive epidemiological overview, future studies should use international classification system as well as consistent inclusion and exclusion criteria. Futher studies are also required to evaluate precisely the impact of fetal cardiac diagnosis on the prevalence and outcome of CHD. Epidemiology of CHD provides an overview of the distribution and characteristics of risk factors. Environmental potential risk factors are reviewed as they may provide an opportunity for prevention of some forms of CHD.