In this study, decolorization of Reactive Blue 220, Acid Red 414 and Basic Yellow 28, decolorization kinetics, and biodegradability of intermediates after ozonolysis were studied. Effect of pH on ozonolysis was studied, and pH 3 was the best among pH values of 3, 7 and 11. The decolorization kinetics of these dyes can be described by a first-order reaction model, and the first-order rate constants of RB 220, AR 414 and BY28 were 0.175-0.1303, 0.164-0.096 and 0.2092-0.1154 min(-1), respectively. Total organic removal was determined to be 24.74, 17.15 and 23.37% for RB220, AR 414 and BY 28, respectively, after 30-min ozonation of 800 mg L-1 dye. The respirometric biologic oxygen demand of Pseudomonas putida (30-min ozone treatment of 800 mg L-1 of dye) was 490, 460 and 451 for RB220, AR 414 and BY 28, respectively. Our results showed that ozonation is an effective way to remove the color from aqueous solutions of these dyes, and that the by-products are non-toxic to P. putida.