A method is provided for mapping electrical activity within a tubular region of or near the heart having a inner circumference, such as a pulmonary vein. The method comprises inserting into the heart a distal end of a mapping catheter. The mapping catheter comprises an elongated tubular catheter body having an outer wall, proximal and distal ends, and at least one lumen extending therethrough. The catheter includes a mapping assembly comprising a tubular structure comprising a pre-formed generally circular main region generally transverse and distal to the catheter body and having an outer circumference. The tubular structure comprises a non-conductive cover over at least the main region of the mapping assembly. A plurality of electrode pairs, each comprising two ring electrodes, are carried by the generally circular main region of the mapping assembly. The method further comprises contacting the outer circumference of the generally circular main region with the inner circumference of the tubular region and mapping the electrical activity within the tubular region with the electrodes along the generally circular main region.