Gives a historical background and describes the chemistry of traditional Japanese colorants. The colour-fastness of several traditional Japanese colorants upon exposure to atmospheric ozone was tested in a chamber. Colorants applied to paper, dyes on silk cloth, and colorants on a 19th-century woodblock print were exposed to 0.40 ppm ozone at 22 degrees C and 50% rh in the absence of light for 12 weeks. Assessment of the effects was made by colour differences calculated from measured diffuse reflectance spectra. Orpiment, indigo, tumeric, safflower, gambodge, and dayflower showed colour loss. Other traditional colorants are listed. Tables, 40 references.