BACKGROUND AND OBJECTIVES: Phased-array intracardiac echocardiography (ICE) is a novel method for monitoring intracardiac procedures. We report our initial experience with ICE for guiding transcatheter device closure of atrial septal defects (ASD). SUBJECTS AND METHODS: From April 2004 to March 2005, ICE was performed in 27 consecutive patients during percutaneous device closure of ASDs. The procedural feasibility, the procedure time, the fluoroscopic time, and the complication rate were compared with 27 prior cases that had utilized transesophageal echocardiography. RESULTS: The procedure was performed successfully in all patients. The total procedure time (PT), device deployment time (DT), and fluoroscopic time (FT) were 65.7+/-22.3, 30.4+/-23.8, and 12.1+/-6.4 minutes for the study group, and 73.6+/-23.7, 29.8+/-16.1, and 11.9+/-6.0 for the control group, respectively, with no significant difference between the groups. However, PT and DT were significantly shorter in the later 14 cases of the study group compared to the 13 initial cases (52.1+/-10.9 and 13.2+/-4.2 vs. 80.3+/-22.4 and 48.8+/-22.2, p<0.01, respectively). These differences were also significant compared to the control group, suggesting that there was a learning curve for the procedure. CONCLUSION: ICE is a feasible and relatively safe method for monitoring and guiding percutaneous transcatheter closure of ASDs, but a learning period can be expected to achieve better proficiency.