The influence of ultraviolet irradiation of different doses (lambda > 300 nm) on the structural and color modifications of cotton fabrics painted with four different azo-triazine dyes (Reactive Yellow 143, Reactive Orange 13, Reactive Red 183, and Reactive Red 2) was studied. High irradiation doses up to 3500 J cm(-2) led to changes in the dyes structures. Structural changes before and after the complete irradiation were compared by applying FTIR, UV-Vis, and near infrared chemical imaging techniques. Color modifications were also investigated. Color differences significantly increased with the irradiation dose for all the studied samples.