The purpose of this study was to investigate the application of trial balloon occlusion for permanent closure of patent ductus arteriosus (PDA) with severe pulmonary hypertension (PH) in adults, and to assess its immediate and short-term results. From September 1999 to September 2005, a total of ten adults (two males, ages ranging from 20 to 54 years) with PDA who met the criterion for severe PH (basal pulmonary vascular resistance >8 Wood units) received trial balloon occlusion via an embolectomy balloon catheter. Post-occlusion hemodynamics, along with an overall clinical and hemodynamic assessment, was used to consider the indication of closure of PDA. Nine of the patients underwent successful transcatheter closure of PDA and subsequently used Amplatzer occluder devices. Chest X-ray, cardiography and echocardiography were used for follow-up evaluation of the treatment within 6 months after successful closure of PDA. No patient had a detectable residual shunt by color flow mapping or any other complications (device migration, hemolysis, endocarditis, etc.) at follow-up. In conclusion, trial balloon occlusion helps to determine anticipated hemodynamics after closure of PDA, so it is conducive to indicating permanent closure of adult PDA with reversible but severe PH. Furthermore, satisfactory immediate and short-term outcomes have proven this method to be safe and valid. (Hypertens Res 2008; 31: 1997-2002).