Several investigators have reported that the presence of calcium may totally preclude resection of plaque material from the lumen of an occluded vessel. Because the authors did not support these findings, they tested the hypothesis and studied the effects of pulsed argon ion laser energy on other non-plaque but dense calcified tissue, such as cortical bone, and found that bone can be cut with ease and safety. Fresh bovine specimens were irradiated with a Spectra Physics model 170 argon ion laser, and the irradiated areas were examined, measured, and photographed.