Removal of dyestuffs by adsorption on to live activated sludge was investigated. Two dyes, one acid dye (Acid Yellow 17) and one basic dye (Maxilon Red BL-N), were tested. Initial adsorption studies showed that binding of Acid Yellow 17 onto activated sludge was not promising while Maxilon Red BL-N was adsorbed well by activated sludge and the dye-sludge system conformed to the Langmuir Model. Kinetic studies were also performed for Maxilon Red and live activated sludge system. According to the results obtained, the initial part of the adsorption followed a first-order process, controlled by film diffusion. Intraparticle diffusion also played a significant role. The kinetics of sorption have been analyzed by three kinetic models, the first order Lagergren model, a pseudo second order model and the second order model. Rate constants for each of the models were derived and correlation coefficients were calculated. The overall process was best described by the pseudo second order model rather than first order model or the second order model. (C) 2002 Elsevier Science Ltd. All rights reserved.