Cyanotic heart defect is a group-type of congenital heart defects (CHDs) that occurs due to deoxygenated blood bypassing the lungs and entering the systemic circulation or a mixture of oxygenated and deoxygenated blood entering the systemic circulation. The prevalence of congenital heart defects (CHDs) in adults has increased during the last decade such that now there are more adults with CHD than children. Advances in the diagnosis and management of CHD appear to be the reason for such a phenomenon. In this review only cyanotic CHD are addressed. The majority are likely to be those that have undergone corrective or palliative surgery, although rarely uncorrected defects may present in adulthood. The most of the cyanotic CHDs presenting in adulthood are likely be those that have undergone palliative or corrective surgery in childhood. Less frequently, previously un-operated patients may present during adult life either because of late detection or due to minimal symptomatology secondary to balanced circulation with a large inter-ventricular communication (or single ventricle) and moderate degree of pulmonary stenosis. As of advances in the diagnosis and management of CHD, many of them are reaching adulthood such that the number of adults with CHD exceeds that in children at the present time and consequently, there are more than one million adults with CHD in USA alone.