UV (XeCl, XeF excimer) and IR (CO, Er:YAG) lasers are of interest for laser angioplasty owing to their restricted light penetration in living tissue, which prevents vascular perforation. The authors investigated the quantitative ablation rate of vascular tissue, both normal and diseased, by IR (CO) and UV (XeCl, XeF) lasers to determine the optimum laser wavelength for which selective ablation is achieved. All experiments were done in vitro. The results show that CO laser radiation preferentially ablates the yellow atheroma with an affinity factor of 1.8. This affinity factor can be attributed to the low melting (and/or vaporizing) point of fatty materials following thermal ablation by the CO laser. However, XeF laser radiation exhibits an inverse affinity (affinity factor of 0.6). A normal layer of the vascular wall contains more proteins than yellow plaque, so that the absorption of UV lasers in the normal vascular wall may be greater than in the plaque.