A catheter for ablating tissue is disclosed that has a self-centering multirayelectrode assembly. The self-centering multiray electrode assembly may have aplurality of spines, each of which a preshaped, expanded configuration thatcurves tochange an orientation of the spine from being directed towards the distal endof catheterbody to being directed towards the proximal end of the catheter body. Theablationelectrodes engage ostial tissue when a maximal outer diameter of the self-centeringmultiray electrode assembly is engaged with an inner diameter of a vessel. Thecompliance of each spine may vary along its length. When the self-centeringmultirayelectrode assembly is engaged within a vessel, the ablation electrodes arebrought intocontact with tissue and may be used to form lesions in a circumferential patharound thevessel.
