Percutaneous laser angioplasty was performed in 19 patients with calcified and non-calcified occlusions (4-25 cm long) of the superficial femoral artery, using a pulsed dye laser at 480 nm and a pulse duration of 2 microseconds per pulse. The treatment laser was guided by a 325 nm diagnostic laser that induced tissue fluorescence. The laser system operated through a single 200 microns optical fiber. Computer spectral analysis of the tissue fluorescence located at the distal end of the fiber tip directed emission of the treatment laser only at the atheroma without affecting the arterial wall. A successful primary laser recanalization was obtained in all cases and was followed by balloon dilation in all but one patient. One mechanical perforation and 2 mechanical arterial dissections by the fiber, and 1 perforation and 1 dissection by the guide wire occurred, but no complications due to the treatment or diagnostic laser were observed. The safety of the procedure seemed to be enhanced by the spectroscopic guidance system which enabled plaque recognition. The pulsed dye treatment laser was well tolerated and effective even in heavily calcified arteries.