The accumulation of calcium onto granular activated carbon (GAC) used for landfill leachate treatment and its effects on the adsorption of 2,4-DCP were studied. A GAC column was installed after the coagulation-sedimentation process of a treatment plant for landfill leachate from a municipal waste landfill site. Major inorganic material accumulated onto the GAC used for landfill leachate treatment was calcium. The accumulation of calcium onto GAC was leveled off in 8 weeks' operation at about 7 mg g(-1), which was much smaller than that reported in drinking water treatment irrespective of the higher concentrations of DOC and calcium in water. The main species of calcium accumulated onto the GAC used for leachate treatment was calcium associated with DOC. Different calcium species in GAC may give different effects on the adsorption capacity of GAC. The accumulation of calcium onto GAC did not decrease the adsorption capacity for 2,4-DCP.