Percutaneous laser angioplasty was performed in 19 patients with total superficial femoral calcified and noncalcified (4 to 25 cm length) occlusions; a pulsed dye laser of 480 nm was used with a pulse duration of 2 musec/pulse. The treatment laser was guided by a 325 nm diagnostic laser that induced fluorescence. The laser system operated through a single 200 or 500 microns optical fiber. Computerized spectral analysis of the tissue fluorescence located at the distal of the fiber tip allowed the treatment laser to be emitted on the atheroma and not on the arterial wall. Uniform success in primary laser recanalization was demonstrated, which allowed for subsequent balloon dilatation in all but one patient. One mechanical fiber perforation, two mechanical fiber dissections, one guidewire perforation, and one guidewire dissection occurred, but no complications resulting from the treatment or diagnostic laser were observed. The safety of the procedure appears to be enhanced by the spectroscopic guidance system, which allows recognition of plaque. The pulsed dye treatment laser was well tolerated and effective even in heavily calcified arteries.