We have performed 50 blade and balloon atrial septostomies in 46 patients with diagnoses of transposition of the great arteries--32 patients; mitral atresia or stenosis--10 patients; total anomalous pulmonary venous drainage--2 patients; tricuspid atresia--1 patient; and pulmonary valve atresia with hypoplastic right ventricle--1 patient. The patients' age ranged from 1 day to 72 months (median = 8 months) and weights ranged from 2.7 to 14.5 kg. In patients with transposition the systemic saturation increased from an average of 62% to 74.6% (p less than 0.001) and the inter-atrial mean pressure gradient was reduced from 7.74 +/- 5.3 to 1.4 +/- 2.04 mm Hg. Patients with mitral atresia had no significant increase in systemic arterial saturation but a significant decrease in the mean inter-atrial gradient from 19.6 +/- 12.4 to 3.8 +/- 5.3 mm Hg. In three patients the blade septostomy was unsuccessful for technical reasons and the condition of the patient. Complications included one death due to atrial laceration, blood loss requiring transfusion in 5 patients, transient CVA in one patient, and failure of the blade to close in one patient. We have found the palliative use of the blade catheter in conjunction with balloon atrial septostomy to be an effective and safe procedure.