Porphyrin-like compounds such as tetra-(4 sulfonatophenyl) porphine (TSPP), chlorin-e6 derivative (CED) and tetrasulfophthalocyanin (TSPC) are photosensitizing agents that absorbed light at 630 nm, 657 nm and 625 nm, respectively, and bind preferentially to atherosclerotic plaque. Porphyrin-treated human cadaveric aorta was compared with untreated aorta using several techniques: the absorptive spectrophotometry which has demonstrated the distinct absorptive peaks at 630 nm, 657 nm, 625 nm in porphyrin-treated plaque which were absent in untreated normal aorta; the fluorescence microscopy, which has shown that the treated atheroma acquired the characteristic fluorescence of porphyrin under ultraviolet light. Because of the porphyrin''s unique property, porphyrin-treated and untreated aorta was exposed to red laser radiation at a wavelength of 632.8 nm. It was found that enhanced photoalteration of porphyrin-treated compared with untreated atheroma. Histologic analysis of the depth of tissue penetration of equal amounts of laser radiation has demonstrated more pronounced photosensitizing effect in TSPC-treated plaque compared with CED-, TSPP-, and untreated plaques. This study demonstrates a potential of tetrasulfophthalocyanin for selective alteration of atheroma by He-Ne laser radiation.