An improved steerable catheter with in-plane deflection comprises a catheter body having proximal and distal ends and a lumen extending therethrough and a tip section at the distal end of the catheter body. The tip section comprises a flexible plastic tubing having a pair of diametrically-opposed lumens extending therethrough. The catheter also provides two puller wires manipulated through a control handle at the proximal end of the catheter body. Each puller wire extends through one of the pair of lumens in the tip section and through the lumen of the catheter body and is anchored to the control handle at its proximal end and anchored to the tip section at its distal end. The deflection mechanism is configured to generally define a plane along which deflection most readily occurs and an edge along which deflection is most readily avoided. The deflection mechanism extends longitudinally along a centerline of the tip section between the first and second puller wire and is configured generally with a cross section having a thinner dimension and a thicker dimension to bias the tip section to deflect in a plane parallel with the thinner dimension of the deflection mechanism and to resist deflection in a plane perpendicular to thicker dimension.
