A method is described for decreasing activity of at least one sympathetic nerve, nerve fiber or neuron innervating at least one blood vessel in the pulmonary vasculature of a patient to ameliorate pulmonary hypertension. In one embodiment, the method may involve advancing an intravascular treatment device to a target location in a target blood vessel within the pulmonary vasculature of the patient and using the treatment device to decrease activity of at least one sympathetic nerve, nerve fiber or neuron innervating the target blood vessel at or near the target location to ameliorate pulmonary hypertension.