Laser angioplasty using a spherical lensed fiber-tip laser delivery catheter and a 200 mum bare silica fiber tip was performed in occluded atherosclerotic iliac arteries of miniature swine. Group I consisted of 8 animals with 11 totally occluded arteries in which the bare silica fiber was used. Group II included 22 animals with occlusive lesions in 41 arteries in which the silica lens tip was used. In vivo laser angioplasty was performed in both groups using an argon ion laser delivering 2 to 3 watts of power in 1 to 5 second intervals. Successful recanalization occurred in 7/11 (64%) in group I arteries and 35/41 (85%) in group II arteries. Vascular perforation occurred in 36% (4/11) in group I compared to 10% (4/41) in group II (P less than 0.05). Mechanical perforation due to the bare fiber alone accounted for 50% of the perforations in group I and did not occur with the silica lens-tip device (group II). We conclude that the atraumatic lensed fiber is more effective in recanalizing occlusive lesions and is a safer delivery system than the bare silica fiber.