An intravascular electrode device for use in neuromodulation includes an anchor expandable from a radially compressed position to a radially expanded position. A lead extends from the anchor and has at least one conductor extending through it. A flex circuit is coupled to the anchor and comprises a flexible insulative substrate, a plurality of electrodes carried by the substrate, and a plurality of conductive traces carried by the substrate, each trace electrically coupled to an electrode and a conductor. Expansion of the anchor within a blood vessel biases the electrodes into contact with the surrounding blood vessel wall. An exemplary anchor includes a first portion having expansion forces sufficient to bias the electrodes against the vessel wall for mapping and chronic stimulation, and a second portion having greater radial expansion forces sufficient to chronically engage the vessel wall once an optimal electrode location has been selected.