Patients with simple congenital heart disease such as isolated atrial septal defects (ASDs) are rapidly becoming a relatively large population with a variety of clinical problems that are often missed by pediatric physicians or grown up congenital heart disease specialists, and may involve different adult health professionals such as general cardiologists or internists. Isolated ASDs are common (7% of all cardiac anomalies) and can present at any age, sometimes in conjunction with other genetic disorders such as Down’s syndrome or in a familiar form. The diagnosis is often accidental: Doppler echocardiography and, recently, magnetic resonance imaging are mandatory to assess types and significance of ASDs. Surgical or percutaneous repair should be offered at any age unless associated with pulmonary vascular disease: Percutaneous closure should be preferred in isolated secundum ASD with sufficient rims on trans-esophageal echocardiography, whereas surgery remains the only option for primum and sinus defects. Follow-up of operated patients is based on Holter EKG and echocardiography that should be scheduled every 2 years for secundum and sinus defects and every year for primum defect with valve repair. ASDs in adolescents and adults may be suspected in any physician’s office and doctors should be acquainted with innovative imaging techniques and contemporary therapeutic options in order to deliver proper care to different types of ASDs and assist them after repair with appropriate follow-up strategies.