Congenital heart disease (CHD) refers to structural or functional abnormalities that are present at birth even though they may manifest later in life. Congenital heart diseases are the most common form of birth defects with 4 to 8 per 1000 live born infants estimated to have a cardiac malformation. We hypothesize that there are ways to subdivide children with CHDs through careful phenotyping of the children and their families. By doing this, one may be able to identify more homogeneous subgroups that will increase the power to detect genetic risk factors. We also anticipate that CHD will be associated with one or more known candidate genes and that novel genes may also be identified which were not previously recognized to play a role in CHD development. Therefore, the primary aim of this study is to better characterize patients with CHD and to evaluate the genetic association between CHD and select candidate genes through transmission disequilibrium testing (TDT). We will also conduct a genome-wide linkage scan once a reasonable number of families with multiple family members with CHD have been enrolled. Additionally, we will survey for environmental risk factors, including maternal preconception and prenatal risk factors, as well as non-cardiac factors that may contribute to the development of CHD.