Optical characteristics of microstructural iridescence in cooked cured beef were studied by transmission and reflectance light microscopy and by fiber optic spectrophotometry. Green iridescence was the most common color in individual muscle fibers. It had a peak spectral emission at 560 nm that was absent from the spectrum of bright green degraded heme pigment. Orange-red iridescence was the next most common color, with a major peak at 650 nm and a secondary peak at 460 nm. When examined microscopically, greenness due to microstructural iridescence disappeared from individual muscle fibers when 1 mm transverse sections of meat were illuminated with transmitted light. In the same sections, iridescent greenness produced by oblique illumination at 45° above the sample surface disappeared at some point when the sample was rotated about its axis.