The rapid small-scale column test (RSSCT) is a scaled-down version of a pilot- or full-scale granular activated carbon (GAC) column. Simple equations for selecting the design and operating parameters of RSSCTs from the full-scale process design variables are presented, and their limitations are discussed. Carbon usage rates and breakthrough profiles for RSSCTs are compared with pilot-column results. Case studies representing high and low levels of synthetic organic chemicals, in the presence and absence of background dissolved organic carbon (DOC), and weakly and strongly adsorbing organics are reviewed; a lengthy table gives results for 22 such studies. For DOC removal, RSSCT and pilot performances were compared for five surface waters and one groundwater. Includes 20 references, tables, figures.