At least a portion of a catheter system (10) is provided with fullerene material (56) for performing or facilitating a medical procedure. In the case of a balloon catheter, the outer surface of the balloon may have a coating of fullerenes (64), which are preferably photosensitive or activated by light. A light source (60) can be used to illuminate or other wise activate the fullerene material. The light source (60) may be formed by one or more optical fibers extending through the shaft of the catheter, and into the balloon. Various arrangements of the catheter system are possible, whereby the light source may selectively emit light outward through the fullerene material, and associated portions of the catheter system, which may be translucent. When activated by light, the fullerene coating may preferably generate, and give off therapeutic oxygen radicals. These oxygen radicals may affect local cell function to prevent or reduce cell proliferation. This therapy may have many applications, including for example, limiting restenosis after angioplasty.