A matched case control study has been conducted in the children's hospitals in Alexandria, Egypt, during 2 years-period, aiming at investigating the risk factors for the occurrence of congenital heart diseases. Our results showed that the significant risk factors for developing any type of congenital heart disease and ventricular septal defects were: older paternal age at birth, positive consanguinity, positive family history, female sex hormones, irradiation, hazardous maternal occupation, diabetes mellitus and suburban or rural residence. However, some environmental/teratogenic factors were not implicated in the etiology of atrial septal defects or pulmonary stenosis. These findings strongly suggest that environmental factors vary according to the specific type of congenital heart disease. This study emphasizes on the need to instruct the public about the importance of pre-marital counseling and the deleterious effects of various teratogens in the environment.