Activated carbon adsorption is widely used in the US for trace organiccompound removal from water. In spite of the wide application of powdered activated carbon (PAC) and granular activated carbon (GAC) for this purpose, there has been a lack of good tools for design and performance prediction for activated carbon systems. This is largely due to the complexity of the competitive effects of natural organic matter (NOM) with the trace compounds in porous adsorbents. In recent years, however, the effect ofNOM on trace organic compound adsorption equilibrium has been successfully described by the equivalent background compound, ideal adsorbed solution theory (EBC-IAST) method. With the EBC-IAST foundation, the adsorption kinetics of trace organic compounds in the presence of NOM has been successfully described by the psuedo-single solute homogeneous surface diffusion model (HSDM). Also, several simplified methods have been developed to predict adsorption from natural water. Based on simple laboratory-scale tests, these methods provide satisfactory prediction of full-scale performance of most PAC systems used for trace organic removal. However, our ability to predict GAC performance for tracecompound removal is still poor due to our limited understanding of various mechanisms at work when water continuously flows through a stationary mass of carbon. This paper reviews the current applications and recent research on GAC and PAC systems in the US water treatment industry, with a focus on the understanding of competitive effects of NOM in trace organic compound adsorption. Includes 39 references, figures.