OBJECTIVE--Assessment of an anterior staircase modification to the standard atrial transseptal technique. DESIGN--Retrospective report on patients undergoing atrial transseptal puncture. SETTING--A regional cardiac centre. PATIENTS--A series of 658 patients catheterised between 1975 and 1991. RESULTS--Needle entry to the left atrium was obtained in 647 (98.3%) patients with needle and catheter entry to the left atrial cavity in 637 patients (96.8%). Sustained atrial arrhythmia occurred in six patients (0.9%) and pronounced bradycardia in one. Cardiac perforation occurred in three patients (0.5%) but did not cause cardiac tamponade. There were no deaths or embolic complications caused by the transseptal puncture. The anterior staircase manoeuvre was particularly useful in patients with problem septa--that is, when the septum bulged into the right atrial cavity, lacked a detectable limbic edge, was tough or tender, or when the right atrium was considerably enlarged. CONCLUSION--The anterior staircase technique is a useful modification to the atrial transseptal puncture technique because it allows repeated passage down the atrial septum without the need for guidewire and needle exchanges for repositioning in the superior vena cava.