The current used parameters for transseptal puncture (TSP) under fluoroscopic guidance is from left atriography and need to be verified by precise anatomic measurement. From February 2009 to July 2013, consecutive patients who received computed tomography (CT) were included. Landmarks and parameters were preliminary studied by right atriography, and further evaluated on the CT images of 1001 patients. A method (CTP-2) was proposed for guiding TSP. In right anterior oblique 45 degrees view, the CTP-2 method was defined by points C, T, and P, and 2 areas: point C is in coronary sinus; point T is at a distance of dCT (usually 1.5 +/- 0.2 vertebral height) over point C; then point P, the optimal puncture site, was located at 0.5 +/- 0.2 vertebral body height posterior to point T; puncture should avoid the aortic root area and the rear triangle area; the aortic root area could be negatively revealed by right atriography at the orifice of inferior vena cava, and the rear triangle area is demarcated by points C, C, and T (C and T are 2 points horizontally posterior to, and at dCT away from points C and T, respectively). The initial application of CTP-2 in 2820 patients showed that it might be helpful in reducing the need of left atriography and the possibility of cardiac perforation.