Researchers evaluated the technical and economic feasibility of renewing exhausted reactive dyebaths via ozonation. The experiment relied on a 'worst case' reactive dye system for coloring cotton knit fabrics in which approximately 50 percent of the dye remained unfixed along with enormous quantities of suspended sodium chloride and sodium sulfate salts. Dyeings were performed in a Unimac Tumbler that rotated at 20 rpm. Heating rates were 5, 2, and 10 degrees Fahrenheit per minute for the wet-out, dyeing, and washing stages, respectively. A Welsbach T-816 ozone generator was attached to a dual column contractor with a total working volume of 10 liters. Tests assessed the effect of changes in temperature, pH, and ozone concentration on results from iodometric measurements during counterflow ozonation. Results showed that the reuse of ozonated water saves chemicals and dramatically reduces fresh water consumption. The quality of dyeings conducted in ozone renewed dyebath water was equivalent to that of dyeing conducted in fresh water. 12 refs.