Angiographic contrast media interference with laser-induced fluorescence excitation and detection in atherosclerotic human coronary arteries. Laser-induced fluorescence has been used in conjunction with angiography for laser angioplasty guidance. The effect of radiopaque contrast media on the excitation and detection of arterial fluorescence has not been previously reported. Accordingly, fluorescence emission spectra from human coronary artery necropsy specimens (n = 7) during excitation with pulsed excimer laser excitation (308 nm) was examined before and after the addition of three different contrast media, sodium and meglumine diatrizoate, sodium and meglumine ioxaglate, and iopamidol. A decrease in overall fluorescence intensity was observed at all wavelengths for each contrast agent examined. The decrease in intensity of fluorescence emission was more marked at wavelengths less than 410 nm than at wavelengths above 425 nm. Similar effects were observed for contrast media diluted with whole blood. Absorption spectra for all three contrast media demonstrated absorption in the ultraviolet centered around 240 nm. We conclude that preferential absorption in the ultraviolet range by contrast media interferes with the excitation and detection of laser-induced fluorescence; use of visible light excitation may obviate interference with laser-induced fluorescence analysis of plaque. 