Introduction: Significant variation exists in the perceived indications for balloon atrial septostomy in children with tricuspid atresia (TA). Many units advocate early, elective balloon atrial septostomy due to potential progressive narrowing of the interatrial opening, especially after the insertion of an arterial shunt. Our practice is to perform an atrial septostomy only in children with clinical and/or echocardiographic features of a restrictive interatrial communication. The aim of the study was to assess our practice by retrospective evaluation of patients born with tricuspid atresia with particular reference to the clinical fate of the atrial septum. More specifically the frequency of emergency atrial septostomy, the complication rate, the need for delayed septostomy or surgical resection and the longer term outcome were evaluated. Materials and methods: The study was a retrospective review (1980–2005) of the data on 49 live-born patients in our departmental database with a diagnosis of TA. One patient was excluded from the study due to referral to another centre and subsequent loss to follow up. By reviewing the medical notes of the remaining 48 patients we collected data on indications for, and timing of balloon atrial septostomy and subsequent complications and long term outcome. Results: The median time to follow up was 9.5 years (0.7–23.7). The diagnosis group was heterogeneous with 38 (79%) patients diagnosed with TA and normally related great arteries with or without pulmonary stenosis or atresia. The remaining 10 patients had more complex anatomy. Of the 48 patients, 5 (10%) were deemed to require balloon atrial septostomy for a clinically and/or echocardiographically restrictive atrial septum. Three procedures were performed within the first 24 hrs of life and 2 within the first month. One of the patients developed NEC following the septostomy and subsequently died of overwhelming sepsis. One patient required delayed surgical septectomy at 6 years of age, during a bidirectional Glenn operation. Of the remaining 42 patients there were 7 deaths (16%) but none were attributed to a restrictive atrial septum (1–at birth, severe acidosis and multi organ failure due to interrupted aortic arch and poor response to IV Prostin; 1–5 days with Group B streptococcal sepsis; 1–post operative sepsis following insertion of a BT shunt; 1–9 years, acute shunt obstruction; 1–withdrawal of care due to complex anatomy deemed to have a poor prognosis; 2-sudden death at home at 3½ years and 11 years). 26 patients required palliation with an arterial shunt (19–modified BT shunt, 6–Waterston Shunt, 1–ductal stent). None of the patients developed a clinically and/or echocardiographically restrictive atrial septum post procedure or during long term follow-up. Conclusions: We conclude that elective balloon atrial septostomy at presentation may not be necessary in patients born with tricuspid atresia. Accepting the limitations of retrospective data collection we also conclude that progressive narrowing of the interatrial septum at a later date is an unusual occurrence, even after an arterial shunt operation. We recommend that atrial septostomy should only be performed in patients who show obvious clinical and/or echocardiographic evidence of restrictive interatrial communication.