Triphenylmethane compounds were exposed in the dark to ozone in air (10 parts per million for 4 days), and the exposed samples were analyzed by mass spectrometry. There was no evidence for reaction between ozone and triphenylmethane and between ozone and the triphenylcarbinol pararosaniline base. In contrast, the triphenylmethane cationic dye Basic Violet 14 yielded substituted benzophenones and other aromatic compounds. These products are consistent with a mechanism involving ozone addition on the unsaturated carbon-carbon bond. The results are briefly discussed in terms of the ozone-fastness of triphenylmethane dyes used as artists' pigments and industrial colorants.