Dyeing wastewater is notorious for its non-readily-biodegradability because it contains various kinds of refractory chemicals. To set up a strategy for controlling the dyeing wastewater discharged into conventional wastewater treatment plants, obtaining bio-kinetic information such as maximum specific growth rate (μmax) and half saturation constant (Ks) should first be done. To estimate the biodegradability of the dyeing wastewater, bio-kinetic constants of the artificially formulated dyeing wastewater containing 33 different dyes and auxiliaries were determined by using a respirometer. Activated sludge acclimated to the artificial dyeing wastewater was inoculated to the respirometer and the bio-kinetic constants were determined from oxygen uptake data. The μmax was found to 0.06 hr.1, which is 3 to 15 times smaller than that of the typical activated sludge for sewage treatment. The Ks was found to 210 mg/L, which was 3.5 to 21 times higher than that of the normal activated sludge.