The objective of this research was to explore alternative activated carbon selection criteria by determining the effects of activated carbon pore structure and surface chemistry on the adsorption of a relatively polar (methyl tertiary-butyl ether [MTBE]) and a relatively nonpolar (trichloroethene [TCE]) trace organic compound in the presence of natural organic matter (NOM). To systematically study the effects of activated carbon pore structure and surface chemistry on adsorption, a matrix of activated carbon fibers (ACFs) was examined. The ACF matrix contained 3 activation levels and 4 surface chemistry levels (acid-washed, oxidized, hydrogen-treated, ammonia-treated). In addition, 3 commercially available granular activated carbons (GACs) were studied [coal-based Filtrasorb 600 (Calgon Carbon Corp.), coconut shell- based G219 (PicaUSA), and wood-based Picazine (PicaUSA)]. Physical and chemical adsorbent characterization included pore structure and surface area determinations by ultra-low pressure N2 adsorption, point of zero charge (PZC) determinations, infrared spectroscopy, and elemental analyses. Adsorption isotherm data for MTBE and TCE were collected in ultrapure water and in San Joaquin Delta Water (SJDW, Concord, CA). Materials and methods for ACF matrix preparation, adsorbent characterization, and isotherm experiments have been described in detail. Includes 3 references, tables, figures.