The stability of thirty-six different commercial dyes in water to visible and ultraviolet light from a carbon arc has been studied. The dyes were selected on the basis of their importance in the textile industry from six major classes: basic, acid, direct, vat, disperse and sulfur dyes. A comparison is made for two of the dyes between laboratory fading rates and fading rates in natural sunlight. Both dyes degraded at least 10 times more rapidly in artificial light than in sunlight. Some previously identified degradation products of Basic Green 4 were confirmed, and a mechanism of their formation was proposed. A significant difference in degradaton rate was observed between water-soluble dyes and pigment dispersions. This study showed that most commercial colors are resistant to photodegradation and many weeks would be required to produce appreciable dye degradation in a natural aquatic environment. (Author)